Birth prevalence of achondroplasia: A systematic literature review and meta-analysis

Dual diagnosis of achondroplasia and mandibulofacial dysostosis with microcephaly

BACKGROUND

Achondroplasia and mandibulofacial dysostosis with microcephaly (MFDM) are rare monogenic, dominant disorders, caused by gain-of-function fibroblast growth factor receptor 3 (FGFR3) gene variants and loss-of-function elongation factor Tu GTP binding domain-containing 2 (EFTUD2) gene variants, respectively. The coexistence of two distinct Mendelian disorders in a single individual is uncommon and challenges the traditional paradigm of a single genetic disorder explaining a patient's symptoms, opening new avenues for diagnosis and management.

CASE PRESENTATION

We present a case of a female patient initially diagnosed with achondroplasia due to a maternally inherited pathogenic FGFR3 variant. She was referred to our genetic department due to her unusually small head circumference and short stature, which were both significantly below the expected range for achondroplasia. Additional features included distinctive facial characteristics, significant speech delay, conductive hearing loss, and epilepsy. Given the complexity of her phenotype, she was recruited to the DDD (Deciphering Developmental Disorders) study and the 100,000 Genomes project for further investigation. Subsequent identification of a complex EFTUD2 intragenic rearrangement confirmed an additional diagnosis of mandibulofacial dysostosis with microcephaly (MFDM).

CONCLUSION

This report presents the first case of a dual molecular diagnosis of achondroplasia and mandibulofacial dysostosis with microcephaly in the same patient. This case underscores the complexity of genetic diagnoses and the potential for coexistence of multiple genetic syndromes in a single patient. This case expands our understanding of the molecular basis of dual Mendelian disorders and highlights the importance of considering the possibility of dual molecular diagnoses in patients with phenotypic features that are not fully accounted for by their primary diagnosis.

The Effectiveness of Growth Modulation Using Tension Band Plates in Children With Achondroplasia in Comparison to Children With Idiopathic Frontal Axial Deformities of the Knee

BACKGROUND

Achondroplasia is the most common form of rhizomelic dwarfism. Aside from disproportionally short extremities, frontal knee malalignments are common. We assessed the effectiveness of guided growth via tension band plates in children with achondroplasia in comparison to patients with idiopathic knee deformities using radiography.

METHODS

Twenty children with achondroplasia (8 valgus/31 varus knees) and 35 children with idiopathic knee malalignments (53 valgus/12 varus knees) which underwent temporary hemiepiphysiodesis at the distal femur and/or proximal tibia were retrospectively compared. Radiographic outcomes (mechanical lateral distal femoral angle, medial proximal tibial angle, and mechanical axis deviation) were compared before surgery and plate removal. Correction rates according to plate location were compared as change per implant duration and per growth in leg length.

RESULTS

Achondroplasia patients were younger (9±2 vs.12±2 y), femoral and tibial growth rate was 43.3% and 48.5% lower and implant duration lasted longer: 36.9±8.9 months in valgus knees and 23.0±14.3 months in varus knees versus 13.4±7.9 months in idiopathic valgus and 11.7±4.6 months in idiopathic varus knees. Significant improvements in joint orientation angles and mechanical axis deviation were achieved but femoral and tibial plates achieved slower correction per months in achondroplasia (P≤0.031). When normalized to bone growth, the rate of correction in joint orientation angles was no longer significantly different for the femur (P=0.241), with a trend for slower correction in the tibia (P=0.066). The corrections in MAD per leg growth (mm/mm) remained smaller (P=0.001). In achondroplasia, older age correlated with slower MAD correction (r=-0.36, P=0.022), femoral plates corrected faster than tibial (P=0.024) and treatment of valgus was less successful than varus involving longer treatments (P=0.009). More complications occurred in achondroplastic knees (P=0.012).

CONCLUSIONS

Skeletally immature patients with achondroplasia can benefit from growth modulations, but they need longer treatments and face more complications. Their slower growth does not solely determine the more tenacious success.

LEVEL OF EVIDENCE

Therapeutic Level III-case-control study.

Clinical outcomes and medical management of achondroplasia in Japanese children: A retrospective medical record review of clinical data

Achondroplasia (ACH) is a rare, autosomal dominant skeletal dysplasia characterized by short stature, characteristic facial configuration, and trident hands. Before vosoritide approval in Japan, patients with ACH could start growth hormone (GH) treatment at age 3 years. However, ACH and its treatment in young Japanese children have not been studied. This retrospective, longitudinal, medical records-based cohort study (before vosoritide approval) summarized symptoms, complications, monitoring, surgery/interventions, and height with/without GH in Japanese patients with ACH <5 years. Complications were observed in 89.2% of all 37 patients; 75.7% required surgery or intervention. All patients were monitored by magnetic resonance imaging; 73.0% had foramen magnum stenosis, while 54.1% had Achondroplasia Foramen Magnum Score 3 or 4. Of 28 GH-treated patients, 22 initiating at age 3 years were generally taller after 12 months versus 9 non-GH-treated patients. Mean annual growth velocity significantly increased from age 2 to 3 versus 3 to 4 years in GH-treated patients (4.37 vs. 7.23 cm/year; p = 0.0014), but not in non-GH-treated patients (4.94 vs. 4.20 cm/year). The mean height at age 4 years with/without GH was 83.6/79.8 cm. These results improve our understanding of young patients with ACH in Japan and confirm that early diagnosis of ACH and monitoring of complications help facilitate appropriate interventions.

Promising horizons in achondroplasia along with the development of new drugs

Achondroplasia (ACH) is a representative skeletal disorder characterized by rhizomelic shortened limbs and short stature. ACH is classified as belonging to the fibroblast growth factor receptor 3 (FGFR3) group. The downstream signal transduction of FGFR3 consists of STAT1 and RAS/RAF/MEK/ERK pathways. The mutant FGFR3 found in ACH is continuously phosphorylated and activates downstream signals, resulting in abnormal proliferation and differentiation of chondrocytes in the growth plate and cranial base synchondrosis. A patient registry has been developed and has contributed to revealing the natural history of ACH patients. Concerning the short stature, the adult height of ACH patients ranges between 126.7-135.2 cm for men and 119.9-125.5 cm for women in many countries. Along with severe short stature, foramen magnum stenosis and spinal canal stenosis are major complications: the former leads to sleep apnea, breathing disorders, myelopathy, hydrocephalus, and sudden death, and the latter causes pain in the extremities, numbness, muscle weakness, movement disorders, intermittent claudication, and bladder-rectal disorders. Growth hormone treatment is available for ACH only in Japan. However, the effect of the treatment on adult height is not satisfactory. Recently, the neutral endopeptidase-resistant CNP analogue vosoritide has been approved as a new drug for ACH. Additionally in development are a tyrosine kinase inhibitor, a soluble FGFR3, an antibody against FGFR3, meclizine, and the FGF2-aptamer. New drugs will bring a brighter future for patients with ACH.

Incidence and Prevalence of Fibrous Dysplasia/McCune-Albright Syndrome: A Nationwide Registry-Based Study in Denmark

CONTEXT

Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare genetic disorder. Incidence and prevalence are not well-studied. Epidemiological research is complicated by the rarity of FD/MAS, absence of registries, heterogeneous presentation, and possibly asymptomatic phenotype. FD/MAS may present with FGF23-mediated hypophosphatemia, of which the epidemiology is also unclear.

OBJECTIVE

Evaluate incidence and prevalence of FD/MAS and FD/MAS-related hypophosphatemia.

METHODS

This cohort study based on the nationwide Danish National Patient Registry from 1995-2018, included patients identified by ICD-10 codes M85.0 (monostotic FD [MFD]) and Q78.1 (polyostotic FD [PFD]/MAS). Incidence rates and prevalence were calculated and stratified by sex, age, calendar period, and diagnosis code. Cases were screened for FD-associated hypophosphatemia by diagnosis code E.83 (disorder of mineral metabolism) and dispatched vitamin D analogues.

RESULTS

A total of 408 patients were identified, 269 with MFD (66%), 139 with PFD/MAS (34%), comparable between sexes. Incidence of FD/MAS demonstrated increasing secular trend with a rate of 3.6 per 1 000 000 person-years (95% CI: 2.9, 4.5) in 2015-2018. Incidence peaked between age 11 and 20. Prevalence of FD/MAS increased over time to 61.0 (95% CI: 54.6, 67.4) per 1 000 000 persons in 2018. The incidence rate of MFD was 1.5-fold that of PFD/MAS in the first decade, rising to 2.5-fold in the last decade. No FD/MAS cases were registered with diagnosis code or treatment for hypophosphatemia.

CONCLUSION

FD/MAS is rare, diagnosis peaks during adolescence without sex predominance, and MFD is most prevalent. Hypophosphatemia may be underdiagnosed and undertreated, or it may be underregistered, comparing this study to literature.

Development of a Weight-Band Dosing Approach for Vosoritide in Children with Achondroplasia Using a Population Pharmacokinetic Model

BACKGROUND AND OBJECTIVE

Vosoritide is a recently approved therapy for achondroplasia, the most common form of disproportionate short stature, that has been shown to be well tolerated and effective in increasing linear growth. This study aimed to develop a population pharmacokinetic (PPK) model to characterize pharmacokinetics (PK) of vosoritide and establish a weight-band dosing regimen.

METHODS

A PPK model was developed using data from five clinical trials in children with achondroplasia (aged 0.95-15 years) who received daily per-kg doses of vosoritide. The model was used to simulate expected exposures in children with a refined weight-band dosing regimen. Simulated exposure was compared with the observed exposure from the pivotal clinical trial to evaluate appropriateness of the weight-band dosing regimen.

RESULTS

A one-compartment model with a change-point first-order absorption and first-order elimination accurately described PK of vosoritide in children with achondroplasia. Body weight was found to be a predictor of vosoritide's clearance and volume of distribution. Additionally, it was observed that dosing solution concentration and duration of treatment influenced bioavailability. The weight-band dosing regimen resulted in simulated exposures that were within the range demonstrated to be well tolerated and effective in the pivotal clinical trial and showed improved consistency in drug exposure across the achondroplasia population.

CONCLUSIONS

The weight-band dosing regimen reduced the number of recommended dose levels by body weight and is expected to simplify dosing for children with achondroplasia and their caregivers.

CLINICAL TRIAL REGISTRATION

NCT02055157, NCT02724228, NCT03197766, NCT03424018, and NCT03583697.

Spinal Postures and Mobility in Children with Achondroplasia vs. Age- and Sex-Matched Healthy Individuals: A Preliminary Report

Background: Achondroplasia is a rare genetic disease, yet the most common form of dwarfism, characterized by limb shortening and disproportionate short stature along with musculoskeletal changes, such as postural deviations. Although postural changes in the spine in children with achondroplasia have been well investigated, little is known about the association of achondroplasia with spinal movements/mobility. Methods: This preliminary study aims to explore the association of achondroplasia with spinal mobility in children with achondroplasia compared to age- and sex-matched healthy individuals. Spinal posture and mobility were assessed using a radiation-free back scan, the Idiag M360 (Idiag, Fehraltorf, Switzerland). Between-group differences were determined using a two-way analysis of variance. Results: Children with achondroplasia had smaller thoracic lateral flexion [difference between groups (Δ) = 20.4°, 95% CI 0.1°-40.6°, p = 0.04], lumbar flexion (Δ = 17.4°, 95% CI 5.5°-29.4°, p = 0.006), lumbar extension (Δ = 14.2°, 95% CI 5.7°-22.8°, p = 0.002) and lumbar lateral flexion (Δ = 19.6°, 95% CI 10.7°-28.4°, p < 0.001) than age- and sex-matched healthy individuals, except for thoracic extension (Δ = 16.5°, 95% CI 4.4°-28.7°, p = 0.009) which was greater in children with achondroplasia. No differences were observed in global spinal postures between the two groups. Conclusions: Spinal mobility appears to be more influenced by achondroplasia than global spinal postures in childhood. These results also highlight the importance of considering the musculoskeletal assessment of segmental spinal postures and rehabilitative interventions aimed at promoting spinal flexibility in children with achondroplasia.

Prophylactic Intramedullary Rodding After Femoral Lengthening in Patients With Achondroplasia and Hypochondroplasia

BACKGROUND

Femoral fracture after femoral lengthening in patients with achondroplasia and hypochondroplasia is a frequent complication, occurring in up to 30%. The purpose of this study is to demonstrate the effectiveness of prophylactic intramedullary rodding in preventing this complication.

METHODS

Multicenter retrospective study involving 86 femoral lengthening procedures in 43 patients with achondroplasia or hypochondroplasia. Forty-two femora (21 patients) were prophylactically managed with intramedullary Rush rodding after external fixation removal (11 females and 10 males, mean age 14.6 years) compared with 44 femora (22 patients) without prophylactic intramedullary rodding (13 females and 9 males, mean age 15.2 years). The mean amount of lengthening in the rodding group was 13.3 cm (52.6%) with an External Fixation Index of 25.8 days/cm; in patients without rodding was 14.3 cm (61.5%) and 24.5 days/cm, respectively.

RESULTS

Seven cases (15.9%) without rodding developed fractures. Four of them required surgical correction due to displacement or shortening. Only 1 patient (2.4%) had fracture of the femur after prophylactic rodding, and surgery was not required. The incidence of femur fracture was significantly lower in the prophylactic rodding group compared with the nonrodding group (2.4% vs. 15.9%, respectively; P =0.034). There were no cases of infection or avascular necrosis.

CONCLUSIONS

Prophylactic intramedullary rodding is a safe and effective method for preventing femoral fractures after femoral lengthening in patients with achondroplasia or hypochondroplasia.

LEVEL OF EVIDENCE

Level III-a retrospective comparative study.

Cervicomedullary Compression in Achondroplasia: A Feared Complication and an Unforeseen Risk Factor of Posterior Circulation Stroke

Achondroplasia is an autosomal dominant disorder with defect in the ossification of the cartilage of long bones. Many bony abnormalities constitute its clinical features, with craniovertebral junction (CVJ) anomalies being one of most common issues which need to be addressed at the earliest. CVJ anomalies in individuals may cause neurovascular compression, which may warrant an early surgery to prevent catastrophic complications. Posterior circulation strokes secondary to CVJ anomalies are well known. We hereby present an unusual case of posterior circulation stroke in an achondroplastic dwarf who presented to our tertiary care centre. Prospective case study. The present case adds to the existing literature about one of the preventable causes of fatal posterior circulation strokes in the young. A high index of suspicion for neurovascular compression at the foramen magnum and early initiation of treatment in achondroplastic young individuals may have gratifying results.

The clinical management of children with achondroplasia in Italy: results of clinician and parent/caregiver surveys

PURPOSE

This study aimed to assess the real-world management of achondroplasia in Italy.

METHODS

Two online surveys addressed to (1) parents/caregivers of individuals with achondroplasia and (2) Italian clinicians managing individuals with achondroplasia were conducted to assess real-world perspectives on achondroplasia management. Both surveys collected data on either patient or clinician demographics, details on diagnoses and referrals, disease complications, and views/experiences with limb lengthening surgery.

RESULTS

In total, 42 parents/caregivers and 19 clinicians (from 18 hospitals) completed the surveys. According to parents/caregivers, achondroplasia diagnosis was most commonly made in the third trimester of gestation (55% of respondents), with a genetic test performed to confirm the diagnosis in all but one case. In contrast, the clinicians indicated that, while achondroplasia was typically suspected during the prenatal period (78%), diagnosis was more frequently confirmed postnatally (72%). Parents/caregivers reported that the greatest impact of achondroplasia-related complications occurred in their children between the ages of 2-5 years. The most significant complications were otitis, sleep apnoea, stenosis of the foramen magnum or pressure on the spinal cord, and hearing difficulties. Lengthening surgery had been presented as a treatment option to 92% of responding parents/caregivers, with 76% of clinicians viewing surgery favourably. Typically, clinicians' reasons for suggesting limb lengthening surgery were to improve patient quality of life, increase patient autonomy and self-acceptance, improve trunk-limb disproportion, short stature and walking, and ensure that all possible treatment options had been presented to the parents/caregivers.

CONCLUSION

This survey provides insight into the real-world management of individuals with achondroplasia in Italy.

Evaluation of simultaneous bilateral femoral distraction osteogenesis with antegrade intramedullary lengthening nails in achondroplasia with rhizomelic short stature: a retrospective study of 15 patients with a minimum follow-up of 2 years

BACKGROUND AND PURPOSE

Bilateral femoral distraction osteogenesis in patients with achondroplasia is insufficiently reported. We aimed to perform the first study that exclusively analyzed simultaneous bilateral femoral distraction osteogenesis with motorized intramedullary lengthening nails via an antegrade approach in patients with achondroplasia focused on reliability, accuracy, precision, and the evolving complications.

PATIENTS AND METHODS

In this retrospective singlecenter study we analyzed patients with achondroplasia who underwent simultaneous bilateral femoral lengthening with antegrade intramedullary lengthening nails between October 2014 and April 2019. 15 patients (30 femoral segments) of median age 14 years (interquartile range [IQR] 12-15) were available for analysis. The median follow-up was 29 months (IQR 27-37) after nail implantation.

RESULTS

The median distraction length per segment was 49 mm (IQR 47-51) with a median distraction index of 1.0 mm/day (IQR 0.9-1.0), and a median consolidation index of 20 days/cm (IQR 17-23). Reliability of the lengthening nails was 97% and their calculated accuracy and precision were 96% and 95%, respectively. The most common complication was temporary restriction of knee range of motion during distraction in 10 of 30 of the lengthened segments. 1 patient was treated with 2 unplanned additional surgeries due to premature consolidation.

CONCLUSION

The method is reliable and accurate with few complications.

Quality of Life in Children With Achondroplasia Undergoing Paired Limb Lengthening With an External Fixator and Modified Distraction Control: Observational Nonrandomized Study

BACKGROUND

Transosseous distraction osteosynthesis is prioritized in orthopedic care for children with achondroplasia. However, difficulties encountered during treatment and rehabilitation directly impact patients' quality of life. Using rod external fixators within a semicircular frame for osteosynthesis is less traumatic compared to spoke circular devices. Their straightforward assembly and mounting on the limb segment can help significantly reduce treatment duration, thereby improving children's quality of life during treatment and rehabilitation.

OBJECTIVE

This study aimed to conduct a comparative analysis of the quality of life (measured by postoperative pain syndrome, physical activity, and emotional state) among children with achondroplasia undergoing paired limb lengthening using either an external fixator with modified distraction control or a circular multiaxial system developed by the authors.

METHODS

This was an observational, prospective, nonrandomized, and longitudinal study with historical control. The study group consisted of 14 patients ranging from 5 to 15 (mean 7.6, SD 2.3) years old with a genetically confirmed diagnosis of achondroplasia. All patients underwent paired limb lengthening with a rod external fixator and a modified distraction control developed by the authors. A total of 28 limb segments, among them 4 (14%) humeri, 8 (29%) femurs, and 16 (57%) tibias, were lengthened in 1 round. Unpublished data from the previous study served as the control group, comprising 9 patients (18 limb segments) of the same age group (mean age at surgery 8.6, SD 2.3 years), who underwent limb lengthening surgery using a circular multiaxial system-2 (11%) humeri, 6 (33%) femurs, and 10 (56%) tibias. The Wong-Baker Faces Rating Scale was used to measure pain symptoms, while the Russified Pediatric Quality of Life (PedsQL) v4.0 questionnaire assessed quality of life.

RESULTS

During the latent phase (7 to 10 days after surgery), a more pronounced decrease in the indicators of physical activity and emotional state on the PedsQL v4.0 questionnaire was noted in the control group (mean 52.4, SD 4.8 versus mean 52.8, SD 5.5 points according to children's responses and their parents' responses, respectively) compared to the experimental group (mean 59.5, SD 6.8 points and mean 61.33, SD 6.5 points according to the children's responses and their parents' responses, respectively). The differences between the groups were statistically significant (P<.05 for children's responses and P<.01 for parents' responses). Importantly, 6 months after surgery, these quality-of-life indicators, as reported by children in the experimental group, averaged 70.25 (SS 4.8) points. Similarly, their parents reported a mean of 70.54 (SD 4.2) points. In the control group, the corresponding values were 69.64 (SD 5.6) and 69.35 (SD 6.2), respectively. There was no statistically significant difference between the groups.

CONCLUSIONS

The external fixator with modified distraction control developed by the authors provides a higher standard of living compared with the circular multiaxial system during the latency phase.

Vosoritide Therapy in Children with Achondroplasia: Early Experience and Practical Considerations for Clinical Practice

INTRODUCTION

Vosoritide is the first precision medical therapy approved to increase growth velocity in children with achondroplasia. Sharing early prescribing experiences across different regions could provide a framework for developing practical guidance for the real-world use of vosoritide.

METHODS

Two meetings were held to gather insight and early experience from experts in Europe, the Middle East, and the USA. The group comprised geneticists, pediatric endocrinologists, pediatricians, and orthopedic surgeons. Current practices and considerations for vosoritide were discussed, including administration practicalities, assessments, and how to manage expectations.

RESULTS

A crucial step in the management of achondroplasia is to determine if adequate multidisciplinary support is in place. Training for families is essential, including practical information on administration of vosoritide, and how to recognize and manage injection-site reactions. Advocated techniques include establishing a routine, empowering patients by allowing them to choose injection sites, and managing pain. Patients may discontinue vosoritide if they cannot tolerate daily injections or are invited to participate in a clinical trial. Clinicians in Europe and the Middle East emphasized the importance of assessing adherence to daily injections, as non-adherence may impact response and reimbursement. Protocols for monitoring patients receiving vosoritide may be influenced by regional differences in reimbursement and healthcare systems. Core assessments may include pubertal staging, anthropometry, radiography to confirm open physes, the review of adverse events, and discussion of concomitant or new medications-but timing of these assessments may also differ regionally and vary across institutions. Patients and families should be informed that response to vosoritide can vary in both magnitude and timing. Keeping families informed regarding vosoritide clinical trial data is encouraged.

CONCLUSION

The early real-world experience with vosoritide is generally positive. Sharing these insights is important to increase understanding of the practicalities of treatment with vosoritide in the clinical setting.

DNA damage in testicular germ cells and spermatozoa. When and how is it induced? How should we measure it? What does it mean?

This review surveys the causes and consequences of DNA damage in the male germ line from spermatogonial stem cells to fully differentiated spermatozoa. Within the stem cell population, DNA integrity is well maintained as a result of excellent DNA surveillance and repair; however, a progressive increase in background mutation rates does occur with paternal age possibly as a result of aberrant DNA repair as well as replication error. Once a germ cell has committed to spermatogenesis, it responds to genetic damage via a range of DNA repair pathways or, if this process fails, by the induction of apoptosis. When fully-differentiated spermatozoa are stressed, they also activate a truncated intrinsic apoptotic pathway which results in the activation of nucleases in the mitochondria and cytoplasm; however, the physical architecture of these cells prevents these enzymes from translocating to the nucleus to induce DNA fragmentation. Conversely, hydrogen peroxide released from the sperm midpiece during apoptosis is able to penetrate the nucleus and induce DNA damage. The base excision repair pathway responds to such damage by cleaving oxidized bases from the DNA, leaving abasic sites that are alkali-labile and readily detected with the comet assay. As levels of oxidative stress increase and these cells enter the perimortem, topoisomerase integrated into the sperm chromatin becomes activated by SUMOylation. Such activation may initially facilitate DNA repair by reannealing double strand breaks but ultimately prepares the DNA for destruction by nucleases released from the male reproductive tract. The abasic sites and oxidized base lesions found in live spermatozoa are mutagenic and may increase the mutational load carried by the offspring, particularly in the context of assisted conception. A variety of strategies are described for managing patients expressing high levels of DNA damage in their spermatozoa, to reduce the risks such lesions might pose to offspring health.

Recommendations for neuroradiological examinations in children living with achondroplasia: a European Society of Pediatric Radiology and European Society of Neuroradiology opinion paper

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise.

Shedding New Light: Novel Therapies for Achondroplasia and Growth Disorders

Achondroplasia is the most common form of disproportionate severe short stature. Management of achondroplasia requires a multidisciplinary approach and has been largely symptomatic for medical complications and psychosocial implications. Increased understanding of genetic and molecular mechanisms of achondroplasia has led to the development of novel disease-modifying drugs. The current drugs under investigation target the growth plate to stimulate chondrocyte growth and development. These include analogs of C-type natriuretic peptide (CNP), FGFR3-selective tyrosine kinase inhibitors, anti-FGFR3 antibodies, aptamers against FGF2, and soluble forms of FGFR3. Long-term data on the effects of these therapies on medical comorbidities are pending at this time.

Sagittal balance parameters in achondroplasia

Introduction

Lumbar spinal stenosis (LSS) is the main problem for adult achondroplasia (Ach). Sagittal imbalance of the spine may play a role in LSS causing neurogenic claudication in Ach patients.

Research question

The purpose of this study is to describe the sagittal balance parameters in Ach patients.

Methods

A single-centre retrospective study of Ach patients that visited the Neurosurgery outpatient clinic of the Leiden University Medical Centre (LUMC) between 2019 and 2022 was performed. We defined sagittal imbalance by a C7 sagittal vertical axis (SVA) of more than 10 mm.

Results

There were 13 patients with a spinal sagittal imbalance and 15 patients with a balanced spine. In both groups, the sacral slope (SS) was comparable (45.0° and 49.0°, p = 0.305), but exceeding the mean SS in non achondroplasts (38.0°). Lumbar lordosis (LL) was more pronounced in the balanced group (55.5° versus 41.7°, p = 0.019), and positively correlated to SS in contrast to the absence of a correlation in the imbalanced group. Thoracolumbar kyphosis (TLK) was increased comparably in both groups (19.6° and 24.6°), and far exceeding the TLK in non achondroplasts (circa 0°), and in both groups negatively correlated with the LL, although not enough to compensate for the smaller LL in the imbalanced group.

Conclusion

Only if the LL compensates for both a larger SS and TLK, the Ach spine can maintain sagittal balance. An explanation for the current data can be the failure of the lumbar spine to give sufficient lordosis due to degenerative processes.

Burden and Treatment of Achondroplasia: A Systematic Literature Review

BACKGROUND

Achondroplasia is the most common form of skeletal dysplasia. Recent advances in therapeutic options have highlighted the need for understanding the burden and treatment landscape of the condition. This systematic literature review (SLR) aimed to identify health-related quality of life (HRQoL)/utilities, healthcare resource use (HCRU), costs, efficacy, safety and economic evaluation data in achondroplasia and to identify gaps in the research.

METHODS

Searches of MEDLINE, Embase, the University of York Centre for Reviews and Dissemination (CRD), the Cochrane Library and grey literature were performed. Articles were screened against pre-specified eligibility criteria by two individuals and study quality was assessed using published checklists. Additional targeted searches were conducted to identify management guidelines.

RESULTS

Fifty-nine unique studies were included. Results demonstrated a substantial HRQoL and HCRU/cost-related burden of achondroplasia on affected individuals and their families throughout their lifetimes, particularly in emotional wellbeing and hospitalisation costs and resource use. Vosoritide, growth hormone (GH) and limb lengthening all conferred benefits for height or growth velocity; however, the long-term effects of GH therapy were unclear, data for vosoritide were from a limited number of studies, and limb lengthening was associated with complications. Included management guidelines varied widely in their scope, with the first global effort to standardise achondroplasia management represented by the International Achondroplasia Consensus Statement published at the end of 2021. Current evidence gaps include a lack of utility and cost-effectiveness data for achondroplasia and its treatments.

CONCLUSIONS

This SLR provides a comprehensive overview of the current burden and treatment landscape for achondroplasia, along with areas where evidence is lacking. This review should be updated as new evidence becomes available on emerging therapies.

Higher rates of non-skeletal complications and greater healthcare needs in achondroplasia compared to the general UK population: a matched cohort study using the CPRD database

BACKGROUND

The natural history of skeletal complications in achondroplasia (ACH) is well-described. However, it remains unclear how the rates of non-skeletal complications, surgical procedures, healthcare needs and mortality differ between individuals with ACH and the general population. This study aimed to contextualise the extent of these outcomes by comparing event rates across the lifespan, between those with ACH and matched controls in a United Kingdom (UK) population.

METHODS

This retrospective, matched cohort study used data from national UK databases: the Clinical Practice Research Database (CPRD) GOLD from primary care, the secondary care Hospital Episode Statistics (HES) databases and the Office of National Statistics mortality records. ACH cases were identified using disorder-specific Read Codes or International Classification of Diseases 10th Revision codes. For each ACH case, up to four age- and sex-matched controls (defined as those without evidence of skeletal/growth disorders) were included. Event rates per 100 person-years were calculated for a pre-defined set of complications (informed by reviews of existing ACH literature and discussion with clinical authors), healthcare visits and mortality. Rate ratios (RRs) with 95% confidence intervals (CIs) were used to compare case and control cohorts.

RESULTS

541 ACH cases and 2052 controls were identified for the CPRD cohort; of these, 275 cases and 1064 matched controls had linkage to HES data. Approximately twice as many non-skeletal complications were reported among individuals with ACH versus controls (RR [95% CI] 1.80 [1.59-2.03]). Among ACH cases, a U-shaped distribution of complications was observed across age groups, whereby the highest complication rates occurred at < 11 and > 60 years of age. Individuals with ACH had greater needs for medication, GP referrals to specialist care, medical imaging, surgical procedures and healthcare visits versus controls, as well as a mortality rate of almost twice as high.

CONCLUSIONS

Patients with ACH experience high rates of a range of both skeletal and non-skeletal complications across their lifespan. To manage these complications, individuals with ACH have significantly increased healthcare needs compared to the general population. These results underscore the need for more coordinated and multidisciplinary management of people with ACH to improve health outcomes across the lifespan.

Real-world evidence in achondroplasia: considerations for a standardized data set

BACKGROUND

Collection of real-world evidence (RWE) is important in achondroplasia. Development of a prospective, shared, international resource that follows the principles of findability, accessibility, interoperability, and reuse of digital assets, and that captures long-term, high-quality data, would improve understanding of the natural history of achondroplasia, quality of life, and related outcomes.

METHODS

The Europe, Middle East, and Africa (EMEA) Achondroplasia Steering Committee comprises a multidisciplinary team of 17 clinical experts and 3 advocacy organization representatives. The committee undertook an exercise to identify essential data elements for a standardized prospective registry to study the natural history of achondroplasia and related outcomes.

RESULTS

A range of RWE on achondroplasia is being collected at EMEA centres. Whereas commonalities exist, the data elements, methods used to collect and store them, and frequency of collection vary. The topics considered most important for collection were auxological measures, sleep studies, quality of life, and neurological manifestations. Data considered essential for a prospective registry were grouped into six categories: demographics; diagnosis and patient measurements; medical issues; investigations and surgical events; medications; and outcomes possibly associated with achondroplasia treatments.

CONCLUSIONS

Long-term, high-quality data are needed for this rare, multifaceted condition. Establishing registries that collect predefined data elements across age spans will provide contemporaneous prospective and longitudinal information and will be useful to improve clinical decision-making and management. It should be feasible to collect a minimum dataset with the flexibility to include country-specific criteria and pool data across countries to examine clinical outcomes associated with achondroplasia and different therapeutic approaches.

Lifetime impact of achondroplasia study in Europe (LIAISE): findings from a multinational observational study

BACKGROUND

Achondroplasia, caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene, is the most common skeletal dysplasia. The Lifetime Impact of Achondroplasia Study in Europe (LIAISE; NCT03449368) aimed to quantify the burden of achondroplasia among individuals across a broad range of ages, including adults.

METHODS

Demographic, clinical and healthcare resource use data were collected from medical records of achondroplasia patients enrolled in 13 sites across six European countries in this retrospective, observational study. Descriptive statistics or event rates per 100 person-years were calculated and compared across age groups as well as by history of limb lengthening. Patient-reported outcomes (quality of life [QoL], pain, functional independence, work productivity and activity impairments) were evaluated using questionnaires at the time of enrolment. An exploratory analysis investigated correlations between height (z-score or centimetres) and patient-reported outcomes.

RESULTS

Overall, 186 study patients were included, with a mean age of 21.7 ± 17.3 years (range 5.0-84.4). At least one complication or surgery was reported for 94.6% and 72.0% of patients, respectively, at a rate of 66.6 and 21.5 events per 100 person-years. Diverse medical and surgical complications were reported for all ages in a bimodal distribution, occurring more frequently in the youngest and oldest age groups. A total of 40 patients had previously undergone limb lengthening (capped at 20% per the study protocol). The most frequent surgery types varied by age, in line with complication profiles. Healthcare resource use was high across all age groups, especially among the youngest and oldest individuals, and did not differ substantially according to history of limb lengthening. Compared to general population values, patients reported impaired QoL particularly for physical functioning domains. In addition, patients reported difficulty carrying out daily activities independently and pain starting in childhood. Patient height correlated with multiple patient-reported outcomes.

CONCLUSIONS

The findings of this study suggest that, across an individual's lifetime, achondroplasia is associated with multisystem complications, reduced QoL and functionality, and increased pain. These results highlight the large amount of healthcare resources that individuals with achondroplasia require throughout their lifespans and provide novel insights into current achondroplasia management practices across Europe. Trial registration ClinicalTrials.gov, NCT03449368, Submitted 14 December 2017 - prospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT03449368.

Fat infiltration in the thigh muscles is associated with symptomatic spinal stenosis and reduced physical functioning in adults with achondroplasia

BACKGROUND

Symptomatic spinal stenosis is a prevalent complication in adults with achondroplasia. Increased muscle fat infiltration (MFI) and reduced thigh muscle volumes have also been reported, but the pathophysiology is poorly understood. We explored whether the increased MFI and reduced thigh muscle volumes were associated with the presence of symptomatic spinal stenosis and physical functioning.

METHODS

MFI and thigh muscle volumes were assessed by MRI in 40 adults with achondroplasia, and compared to 80 average-statured controls, matched for BMI, gender, and age. In achondroplasia participants, the six-minute walk-test (6MWT), the 30-s sit-to-stand test (30sSTS), and a questionnaire (the IPAQ) assessed physical functioning.

RESULTS

Symptomatic spinal stenosis was present in 25 of the participants (the stenosis group), while 15 did not have stenosis (the non-stenosis group). In the stenosis group, 84% (21/25) had undergone at least one spinal decompression surgery. The stenosis group had significantly higher MFI than the non-stenosis group, with an age-, gender and BMI-adjusted difference in total MFI of 3.3 percentage points (pp) (95% confidence interval [CI] 0.04 to 6.3 pp; p = 0.03). Compared to matched controls, the mean age-adjusted difference was 3.3 pp (95% CI 1.7 to 4.9 pp; p < 0.01). The non-stenosis group had MFI similar to controls (age-adjusted difference - 0.9 pp, 95% CI - 3.4 to 1.8 pp; p = 0.51). MFI was strongly correlated with the 6MWT (r = - 0.81, - 0.83, and - 0.86; all p-values < 0.01), and moderately correlated with the 30sSTS (r = - 0.56, - 0.57, and - 0.59; all p-values < 0.01). There were no significant differences in muscle volumes or physical activity level between the stenosis group and the non-stenosis group.

CONCLUSION

Increased MFI in the thigh muscles was associated with the presence of symptomatic spinal stenosis, reduced functional walking capacity, and reduced lower limb muscle strength. The causality between spinal stenosis, accumulation of thigh MFI, and surgical outcomes need further study. We have demonstrated that MRI might serve as an objective muscle biomarker in future achondroplasia studies, in addition to functional outcome measures. The method could potentially aid in optimizing the timing of spinal decompression surgery and in planning of post-surgery rehabilitation.

Australian guidelines for the management of children with achondroplasia

Achondroplasia is the most common form of skeletal dysplasia. In addition to altered growth, children and young people with achondroplasia may experience medical complications, develop and function differently to others and require psychosocial support. International, European and American consensus guidelines have been developed for the management of achondroplasia. The Australian focused guidelines presented here are designed to complement those existing guidelines. They aim to provide core care recommendations for families and clinicians, consolidate key resources for the management of children with achondroplasia, facilitate communication between specialist, local teams and families and support delivery of high-quality care regardless of setting and geographical location. The guidelines include a series of consensus statements, developed using a modified Delphi process. These statements are supported by the best available evidence assessed using the National Health and Medicine Research Council's criteria for Level of Evidence and their Grading of Recommendations Assessment, Development and Evaluation (GRADE). Additionally, age specific guides are presented that focus on the key domains of growth, medical, development, psychosocial and community. The guidelines are intended for use by health professionals and children and young people with achondroplasia and their families living in Australia.

Growth parameters in children with achondroplasia: A 7-year, prospective, multinational, observational study

PURPOSE

This study was undertaken to collect baseline growth parameters in children with achondroplasia who might enroll in interventional trials of vosoritide, and to establish a historical control.

METHODS

In this prospective, observational study, participants (≤17 years) underwent a detailed medical history and physical examination and were followed every 3 months until they finished participating in the study by enrolling in an interventional trial or withdrawing.

RESULTS

A total of 363 children were enrolled (28 centers, 8 countries). Mean (SD) follow up was 20.4 (15.0) months. In participants <1 year, mean annualized growth velocity (AGV) was 11.6 cm/year for girls and 14.6 cm/year for boys. By age 1 year, mean AGV decreased to 7.4 cm/year in girls and 7.1 cm/year in boys. By age 10 years, mean AGV decreased to 3.6 cm/year for both sexes. Mean height z-score in participants <1 year was -2.5 for girls and -3.2 for boys and decreased up to the age 5 years (-5.3 for girls; -4.6 for boys). Girls and boys had a disproportionate upper-to-lower body segment ratio. Mean ratio was highest in participants aged <1 year (2.9 for girls; 2.8 for boys) and decreased gradually to approximately 2 in both sexes from 4 years of age onward.

CONCLUSION

This study represents one of the largest datasets of prospectively collected medical and longitudinal growth data in children with achondroplasia. It serves as a robust historical control to measure therapeutic interventions against and to further delineate the natural history of this condition.

Achondroplasia: Update on diagnosis, follow-up and treatment

Achondroplasia requieres multidisciplinary follow-up, with the aim of preventing and managing complications, improving the quality of life of people who suffer from it and favoring their independence and social inclusion. This review is justified by the multiple publications generated in recent years that have carried out a change in its management. Different guidelines and recommendations have been developed, among which the one made by the American Academy of Pediatrics in 2005 recently updated (2020), the Japanese guide (2020), the first European Consensus (2021) and the International Consensus on the diagnosis, approach multidisciplinary approach and management of individuals with achondroplasia throughout life (2021). However, and despite these recommendations, there is currently a great worldwide variability in the management of people with achondroplasia, with medical, functional and psychosocial consequences in patients and their families. Therefore, it is essential to integrate these recommendations into daily clinical practice, taking into account the particular situation of each health system.

Epidemiology of Eustachian tube dysfunction and related otologic diagnoses among children with achondroplasia

OBJECTIVE

To investigate the prevalence of diagnosed Eustachian tube dysfunction and related otologic diagnoses among children with achondroplasia as compared to a control population.

METHODS

The TriNetX Analytics Network, a federated health research network that aggregates the de-identified electronic health record data of over 78 million patients across the United States, was queried for patients 18 years old or younger with achondroplasia. Patients in this group with any occurrence of diagnosed Eustachian tube dysfunction or specified otologic diagnoses were recorded and reported.

RESULTS

Out of 2,195 patients 18 years old or younger with diagnosed achondroplasia, 379 (17.27%, 95% CI: 15.71-18.91) had a diagnosis of Eustachian tube dysfunction with an 8.65 (95% CI: 7.89-9.48) times higher risk than children without achondroplasia (n = 12,818,655). Children with achondroplasia also had higher risks for diagnosed otitis media (RR: 2.21), tympanic membrane retraction (RR: 7.29), middle ear cholesteatoma (RR: 6.35), cleft palate (RR: 12.24), conductive hearing loss (RR: 12.15), and tympanostomy tube placement (RR: 9.71). Each increased risk was maintained when cleft palate patients were removed from the achondroplasia group.

CONCLUSION

Children with achondroplasia are at a significantly higher risk for diagnosed Eustachian tube dysfunction and related middle ear diagnoses. Atypical craniofacial anatomy among children with achondroplasia may play a role in the dysfunction of the Eustachian tube and thus the observed epidemiology of otologic conditions. Children with achondroplasia should be monitored closely for middle ear conditions and the constellation of symptoms related to a dysfunctional Eustachian tube.

Phase 1 safety, tolerability, pharmacokinetics and pharmacodynamics results of a long-acting C-type natriuretic peptide prodrug, TransCon CNP

AIM

TransCon CNP is a novel prodrug designed to provide sustained release of C-type natriuretic peptide (CNP) for once-weekly therapy, addressing the pathology leading to aberrant skeletal development in achondroplasia. This phase 1 trial was initiated to assess the safety, tolerability, pharmacodynamics (PD) and pharmacokinetics (PK) of TransCon CNP.

METHODS

This randomized, placebo-controlled, single-ascending dose phase 1 trial was performed at two sites in Australia and enrolled 45 healthy adult males. Subjects received placebo or TransCon CNP (single-ascending dose cohorts [3, 10, 25, 75 or 150 μg CNP/kg]). The primary endpoint was frequency of adverse events and other safety outcomes. Other endpoints included PK and PD measured by cyclic guanosine-monophosphate (cGMP) and amino-terminal propeptide of CNP (NTproCNP).

RESULTS

TransCon CNP provided continuous systemic exposure to CNP over at least 7 days post-dose. Plasma and urine levels of cGMP were significantly increased in subjects administered TransCon CNP at 75-150 μg CNP/kg, indicating target engagement of active CNP at the natriuretic peptide receptor-B (NPR-B) for at least 1 week post-dose. TransCon CNP was well-tolerated, with no serious treatment-emergent adverse events or discontinuations. Extensive cardiac safety assessments did not reveal any clinically relevant effects on electrocardiogram parameters, including heart rate, PR, QRS and QTcF intervals.

CONCLUSIONS

Safety and PD data from this phase 1 trial support that TransCon CNP is well tolerated, with a PK profile compatible with a once-weekly dosing regimen. Further studies are ongoing to evaluate the potential of TransCon CNP to positively impact abnormal endochondral ossification in children with achondroplasia.

Associated anomalies in cases with achondroplasia

Associated congenital anomalies may be observed in cases with achondroplasia. The prevalence reported in the literature and the types of co-occurring congenital anomalies are variable between the reported studies. The aim of this study was to establish the prevalence and to describe the associated anomalies in cases with achondroplasia. This study included 25 cases ascertained from our registry of congenital anomalies including all terminations of pregnancy, stillbirths and live births between 1979 and 2007 in 387,067 consecutive births (the prevalence of achondroplasia was 6.4 per 100,000 births), and 223 cases ascertained from the French Little People organization built on the model of LPA (Little People of America, Inc.). Out of these 248 cases of achondroplasia 37 (14.9%) had associated anomalies including 4 (1.6%) cases with chromosomal abnormalities (2 trisomies 21, one 22 q11.2 deletion, and one 47, XXX), 2 (0.8%) cases with recognizable non-chromosomal conditions (one Moebius syndrome and one Pierre Robin sequence) and 31(12.5%) cases with MCA (multiple congenital anomalies). The 31 cases with MCA had 45 anomalies. Anomalies in the urogenital system (24.4%), the cardiovascular system (20.0%), the musculoskeletal system (15.5%), the central nervous system (11.1%), the eye (11.1%), and the orofacial system (8.8%) were the most common MCA. The overall prevalence of associated anomalies shows that the individuals with achondroplasia need a careful screening for other congenital anomalies.

Comprehensive literature review on the prevalence of comorbid conditions in patients with achondroplasia

BACKGROUND

Achondroplasia (ACH) is a rare, genetic condition and is the most common skeletal dysplasia resulting in disproportionate short stature and numerous multi-systemic comorbidities. As we enter an era of new treatment options which may impact comorbidities, it is important to understand the background rates of these events to aid evaluation of potential treatment effects. Thus, the aim of this literature review was to provide a comprehensive quantification of prevalence estimates of comorbidities in achondroplasia by age for use as a compiled reference to assist in quantifying the risk/benefit of new treatment options and informing timely management of ACH.

METHODS

PubMed and Embase databases were searched, complemented by manual bibliography searching, for peer-reviewed articles published between 1975 and 2021, guided by PRISMA principles. Number of patients and the prevalence of specific comorbidities by age were extracted. We calculated exact 95 %-confidence limits for the proportion of affected patients (prevalence) and data were presented visually using forest plots. An a priori decision was made not to utilise meta-analytic techniques to pool estimates as we intended to understand the variability in comorbidities by displaying each estimate separately.

RESULTS

The literature search identified 206 articles of which 73 were eligible for inclusion. The majority of studies (n = 34) had been conducted in the USA or in Europe (n = 20). Study designs were mostly retrospective chart reviews (n = 33) or small cohort studies (n = 19). The availability of literature on particular conditions varied but trended towards a focus on assessment and prevention of severe conditions, such as respiratory conditions in children (21 studies), neurological manifestations (16 studies) and upper spine compression (15 studies). There was substantial heterogeneity in study design, type of clinical setting, populations and use of definitions in reporting comorbidities which need to be considered when interpreting study results. Despite the variability of the studies, comorbidity patterns by age were recognizable. In infants, a high prevalence (>20 %) was found for kyphosis, a range of neurological manifestations and sleep apnea. There was also an excess mortality in infancy (4-7.8/100 person-years). Conditions identified in infancy continued to prevail in childhood. Genu varum was highly prevalent from the age children started to walk (9-75 %). Other conditions started to emerge in children; those with a high prevalence (>20 %) were hearing loss and pain. In adolescence, neurological manifestations in the arm, neck or leg were reported (~15 %), consistent with symptomatic spinal stenosis or spinal compression. Fewer studies were available in older populations, especially in adults; however limited data suggest that pain and cardiovascular conditions, particularly excess weight and obesity, became more prevalent into adulthood. Mortality rates increased again in older age-groups.

CONCLUSION

This review provides a reference base of current knowledge of the type and frequency of comorbidities in ACH. This not only allows future contextualisation of new treatment options but supports clinical decision-making on the timely medical management and intervention of ACH. This review also reflects the current medical priorities in the management of ACH, indicating a focus on pediatric care and the complex needs of individuals with ACH involving many different disciplines. Further studies into the natural history of this rare disease using more consistent definitions of comorbidities, especially into adulthood, are needed to elucidate the multi-systemic nature of this condition.

National burden of achondroplasia: an analysis of the National Inpatient and Nationwide Ambulatory Surgery Samples

Background: To estimate the cost of US hospital admissions and outpatient surgeries associated with achondroplasia. Materials & methods: Using 2017 data from nationally representative databases, this study identifies hospital admissions and outpatient encounters with an achondroplasia diagnosis. Descriptive measures are reported. Results: There were 1985 achondroplasia admissions nationwide. The most frequent admissions were neonatal care (33.7%) in children and musculoskeletal (22.7%) in adults. Average hospital length of stay was 6.8 days, 2.2 days longer than the US mean. Total mean inpatient costs were US$19,959, $7789 greater than the US mean. In the outpatient setting, children 5-14 years accounted for 56.9% of procedures. Conclusion: Achondroplasia is a serious condition with a wide range of lifelong complications frequently requiring hospitalization and surgical intervention.

Medical complications in children with achondroplasia

AIM

To determine the rates of medical investigations, complications, interventions, and outcomes in children with achondroplasia.

METHOD

Children and adolescents with achondroplasia born between 2000 and 2019, aged between 0 and 18 years of age, and seen at The Children's Hospital at Westmead skeletal dysplasia clinic were included. Data were collected retrospectively from clinical records. Standard descriptive statistics were used for analysis.

RESULTS

The study included 108 participants, 58 males and 50 females. Ninety-nine participants (91.7%) entered the study at birth. The other nine (8.3%) participants entered the study after birth (mean age = 2 years 4 months, SD = 1 year 8 months). The median age of exit from the study was 8 years 8 months (IQR = 8 years 9 months) with a median follow-up of 8 years 8 months (IQR = 8 years 9 months). Fifty-two (48%) participants presented with craniocervical stenosis, 15 (13.9%) with hydrocephalus, 66 (61.1%) with hearing impairment, 44 (40.7%) with sleep-disordered breathing, 46 (42.6%) with lower-limb malalignment, 24 (22.2%) with thoracolumbar kyphosis, 10 (9.3%) with symptomatic spinal stenosis, 12 (11.1%) with obesity, and 16 (14.8%) who had at least one admission for respiratory illness. Two children died during the study period.

INTERPRETATION

We report contemporary rates of medical complications in an Australian population of children with achondroplasia. Recommendations for surveillance in clinical practice are discussed. This information will help guide clinicians with their expectant management of achondroplasia and provide prognostic information to the families of children with achondroplasia.

Optimising the diagnosis and referral of achondroplasia in Europe: European Achondroplasia Forum best practice recommendations

BACKGROUND

Achondroplasia is the most common form of skeletal dysplasia, with serious comorbidities and complications that may occur from early infancy to adulthood, requiring lifelong management from a multidisciplinary team expert in the condition The European Achondroplasia Forum guiding principles of management highlight the importance of accurate diagnosis and timely referral to a centre specialised in the management of achondroplasia to fully support individuals with achondroplasia and their families, and to appropriately plan management. The European Achondroplasia Forum undertook an exploratory audit of its Steering Committee to ascertain the current situation in Europe and to understand the potential barriers to timely diagnosis and referral.

RESULTS

Diagnosis of achondroplasia was primarily confirmed prenatally (66.6%), at Day 0 (12.8%) or within one month after birth (12.8%). For suspected and confirmed cases of achondroplasia, a greater proportion were identified earlier in the prenatal period (87.1%) with fewer diagnoses at Day 0 (5.1%) or within the first month of life (2.6%). Referral to a specialist centre took place after birth (86.6%), predominantly within the first month, although there was a wide variety in the timepoint of referral between countries and in the time lapsed between suspicion or confirmed diagnosis of achondroplasia and referral to a specialist centre.

CONCLUSIONS

The European Achondroplasia Forum guiding principles of management recommend diagnosis of achondroplasia as early as possible. If concerns are raised at routine ultrasound, second line investigation should be implemented so that the diagnosis can be reached as soon as possible for ongoing management. Clinical and radiological examination supported by molecular testing is the most effective way to confirm diagnosis of achondroplasia after birth. Referral to a centre specialised in achondroplasia care should be made as soon as possible on suspicion or confirmation of diagnosis. In countries or regions where there are no official skeletal dysplasia reference or specialist centres, priority should be given to their creation or recognition, together with incentives to improve the structure of the existing multidisciplinary team managing achondroplasia. The length of delay between diagnosis of achondroplasia and referral to a specialist centre warrants further research.

A long-acting C-natriuretic peptide for achondroplasia

The C-natriuretic peptide (CNP) analog vosoritide has recently been approved for treatment of achondroplasia in children. However, the regimen requires daily subcutaneous injections in pediatric patients over multiple years. The present work sought to develop a long-acting CNP that would provide efficacy equal to or greater than that of vosoritide but require less frequent injections. We used a technology for half-life extension, whereby a drug is attached to tetra-polyethylene glycol hydrogels (tetra-PEG) by β-eliminative linkers that cleave at predetermined rates. These hydrogels-fabricated as uniform ∼60-μm microspheres-are injected subcutaneously, where they serve as a stationary depot to slowly release the drug into the systemic circulation. We prepared a highly active, stable CNP analog-[Gln^6,14]CNP-38-composed of the 38 C-terminal amino acids of human CNP-53 containing Asn to Gln substitutions to preclude degradative deamidation. Two microsphere [Gln^6,14]CNP-38 conjugates were prepared, with release rates designed to allow once-weekly and once-monthly administration. After subcutaneous injection of the conjugates in mice, [Gln^6,14]CNP-38 was slowly released into the systemic circulation and showed biphasic elimination pharmacokinetics with terminal half-lives of ∼200 and ∼600 h. Both preparations increased growth of mice comparable to or exceeding that produced by daily vosoritide. Simulations of the pharmacokinetics in humans indicated that plasma [Gln^6,14]CNP-38 levels should be maintained within a therapeutic window over weekly, biweekly, and likely, monthly dosing intervals. Compared with vosoritide, which requires ∼30 injections per month, microsphere [Gln^6,14]CNP-38 conjugates-especially the biweekly and monthly dosing-could provide an alternative that would be well accepted by physicians, patients, and patient caregivers.

International Consensus Statement on the diagnosis, multidisciplinary management and lifelong care of individuals with achondroplasia

Achondroplasia, the most common skeletal dysplasia, is characterized by a variety of medical, functional and psychosocial challenges across the lifespan. The condition is caused by a common, recurring, gain-of-function mutation in FGFR3, the gene that encodes fibroblast growth factor receptor 3. This mutation leads to impaired endochondral ossification of the human skeleton. The clinical and radiographic hallmarks of achondroplasia make accurate diagnosis possible in most patients. However, marked variability exists in the clinical care pathways and protocols practised by clinicians who manage children and adults with this condition. A group of 55 international experts from 16 countries and 5 continents have developed consensus statements and recommendations that aim to capture the key challenges and optimal management of achondroplasia across each major life stage and sub-specialty area, using a modified Delphi process. The primary purpose of this first International Consensus Statement is to facilitate the improvement and standardization of care for children and adults with achondroplasia worldwide in order to optimize their clinical outcomes and quality of life.

Experiences of children and adolescents living with achondroplasia and their caregivers

Background

Achondroplasia, caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene (FGFR3), leads to significant multisystem complications across the lifespan that may affect the health‐related quality of life (HRQoL) of individuals and families living with the condition.

Methods

The objective of this qualitative study was to describe the HRQoL of children and adolescents with achondroplasia and their caregivers. Thirty‐four caregivers and 12 adolescents from the United States and Spain participated in one of eight focus groups or completed an individual interview, which was audio‐recorded and transcribed. Thematic analysis of qualitative data was performed to identify commonly occurring themes pertaining to HRQoL.

Results

Caregivers and adolescents described challenges with physical functioning and medical complications due to achondroplasia. Key challenges included difficulties performing activities of daily living, issues of accessibility, bullying, or unwanted attention in public, and negative effects on self‐esteem. Caregivers were concerned about accessing appropriate medical care for their child, and also reported experiencing financial, relational, and emotional challenges in their families. Achondroplasia also affected individuals and their families in positive ways, including increasing empathy, receiving positive attention, and feeling supported by the achondroplasia community.

Conclusions

These findings underscore the importance of regular assessments of HRQoL and the provision of psychosocial support to affected children and families.

Impact of achondroplasia on Latin American patients: a systematic review and meta-analysis of observational studies

Background

Achondroplasia (ACH), the most common form of disproportionate short stature, is caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene. Recent advances in drug therapy for ACH have highlighted the importance of elucidating the natural history and socioeconomic burden of this condition. Recognition that there are many potential issues for the patient with ACH is the first step in planning cost-effective interventions in Latin America (LATAM), a vast geographic territory comprising countries with multicultural characteristics and wide socioeconomic differences. We conducted a systematic literature review to characterize the impact of ACH on affected individuals and on healthcare resources in LATAM countries.

Methods

Searches of the global medical literature as well as regional and local medical literature up to August 2020. Observational studies on patients with ACH from any LATAM country. Pairs of reviewers independently screened eligible articles, extracted data from included studies, and assessed their risk of bias.

Results

Fifty-three unique studies (28 case series and cross-sectional studies and 25 case reports) including data on 1604 patients were eligible. Of these studies, 11 had data available for meta-analysis. Both premature mortality and all-cause mortality in the pooled studies was 15% [95% Confidence Interval (CI) 1.0E−3 to 0.47; I² = 82.9%, p = 0.0029; three studies, n = 99 patients]. Frequency of cardio-respiratory-metabolic disorders was 17% [95% CI 0.04–0.37; I² = 90.3%, p < 0.0001; four studies, n = 230 patients]; nervous system disorders was 18% [95% CI 0.07–0.33; I² = 84.6%, p < 0.0001; six studies, n = 262 patients]; ear, nose, throat and speech disorders was 32% [95% CI 0.18–0.48; I² = 73.4%, p = 0.0046; five studies, n = 183 patients]; and spinal issues including stenosis, compression and associated pain was 24% [95% CI 0.07–0.47; I² = 91.3%, p < 0.0001; five studies, n = 235 patients].

Conclusions

There is currently evidence of high clinical burden in ACH patients in LATAM countries. Establishing the impact of ACH provides the necessary foundation for planning tailored and effective public health interventions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02142-3.

Treatment Goals for Achondroplasia: A Qualitative Study with Parents and Adults

INTRODUCTION

Achondroplasia is characterized by disproportionate short stature accompanied by other changes to the musculoskeletal system. Individuals with this condition typically experience a variety of medical complications. As pharmacologic treatments continue to be developed for the treatment of achondroplasia, it is important to understand treatment goals among those affected by achondroplasia and the factors that shape their goals.

METHODS

This qualitative study is based on semi-structured interviews with 19 parents of children with achondroplasia and five adults with achondroplasia in the USA. We employed thematic analysis using an iterative process to identify themes across the interviews.

RESULTS

Participants had two goals for pharmacologic treatment of achondroplasia: ameliorating complications associated with the condition and increasing stature to overcome functional limitations and psychosocial challenges. Complications of particular concern were chronic pain and surgeries to repair spinal, ear, nose, and throat (ENT) problems, and neurological sequelae. Increased height would enhance independence, help individuals to fit in socially, and avoid social stigma. Countervailing factors included the importance of stature to their identity and the concern that the condition would remain despite treatment.

CONCLUSIONS

This study offers evidence about how individuals affected by achondroplasia think about the pharmacologic treatment of this condition, including both the benefits of ameliorating complications and increasing height. The findings can offer practical insights for parents of children considering treatment, treating physicians, and decision-makers evaluating coverage decisions for treatment of achondroplasia.

Quality of life, physical functioning, and psychosocial function among patients with achondroplasia: a targeted literature review

PURPOSE

Achondroplasia (ACH) is the most common form of skeletal dysplasia, resulting in disproportionate short stature and medical complications. We review the literature on physical functioning, psychosocial function, and quality of life (QoL) in ACH individuals compared to average stature individuals or other short stature conditions. Studies that assess the association between these outcomes and height, limb length/lengthening surgery in ACH patients are also summarized.

MATERIALS AND METHODS

PubMed/MEDLINE and Embase were searched through April 2021. Study inclusion criteria were: (1) quantitative design; (2) study population consisting solely/mainly of ACH patients; (3) reports of physical functioning, psychosocial functioning, and/or QoL. Included studies were summarized separately for pediatric and adult populations.

RESULTS

Of 1664 records identified, 23 primary studies (sample size 8-437 participants) were included. Multiple tools were used across studies, including the generic PedsQL and SF-36 and height-specific QoLISSY.

CONCLUSIONS

The literature demonstrates that ACH patients experience limitations in physical functioning and poorer QoL outcomes compared to average stature people across the life span. This appeared to be at least in part due to disproportionate short stature. Future research to better characterize QoL in ACH patients will assist clinicians to better evaluate the effectiveness of management programs including novel interventions.IMPLICATIONS FOR REHABILITATIONPatients with achondroplasia experience limitations in physical functioning and poorer quality of life throughout their life course when compared to average statured individuals.Psychosocial issues are also heightened in adults with achondroplasia compared to average statured peers but are observed less frequently in children and adolescents with achondroplasia.The overall impact that limb lengthening has on physical functioning and QoL remains unclear, although there is some evidence that greater height or upper limb length may lead to an improvement in these parameters.Rehabilitation professionals should regularly assess physical functioning, psychosocial wellbeing, and quality of life in individuals with achondroplasia using condition-specific tools.

The first European consensus on principles of management for achondroplasia

Achondroplasia is the most common type of skeletal dysplasia, caused by a recurrent pathogenic variant in the fibroblast growth factor receptor 3 (FGFR3). The management of achondroplasia is multifaceted, requiring the involvement of multiple specialties across the life course. There are significant unmet needs associated with achondroplasia and substantial differences in different countries with regard to delivery of care. To address these challenges the European Achondroplasia Forum (EAF), a network of senior clinicians and orthopaedic surgeons from Europe and the Middle East representative of the achondroplasia clinical community, came together with the overall aim of improving patient outcomes. The EAF developed a consensus on guiding principles of management of achondroplasia to provide a basis for developing optimal care in Europe. All members of the EAF were invited to submit suggestions for guiding principles of management, which were consolidated and then discussed during a meeting in December 2020. The group voted anonymously on the inclusion of each principle, with the requirement of a 75% majority at the first vote to pass the principle. A vote on the level of agreement was then held. A total of six guiding principles were developed, which cover management over the lifetime of a person with achondroplasia. The principles centre on the lifelong management of achondroplasia by an experienced multidisciplinary team to anticipate and manage complications, support independence, and improve quality of life. There is focus on timely referral to a physician experienced in the management of achondroplasia on suspicion of the condition, shared decision making, the goals of management, access to adaptive measures to enable those with achondroplasia to access their environment, and the importance of ongoing monitoring throughout adolescence and adulthood. All principles achieved the 75% majority required for acceptance at the first vote (range 91–100%) and a high level of agreement (range 8.5–9.6). The guiding principles of management for achondroplasia provide all healthcare professionals, patient advocacy groups and policy makers involved in the management of achondroplasia with overarching considerations when developing health systems to support the management of achondroplasia.

Achondroplasia: Clinical, Radiological and Molecular Profile from Rare Disease Centre, India

Achondroplasia is the most common autosomal dominant form of skeletal dysplasia and is caused by heterozygous mutations of the fibroblast growth factor receptor 3 ( FGFR3 ) gene at region 4p16.3. This study highlights the data of achondroplasia cases, clinical spectrum, and their outcome from small cities and the region around Rajasthan. The data for analysis were collected retrospectively from genetic records of rare disease clinic in Rajasthan. Clinical profile, radiographic features, molecular test results, and outcome were collected. There were 15 cases, including eight males and seven females, in this cohort. All had facial hypoplasia, depressed nasal bridge, prominent forehead, and characteristic radiographic features. A total of 14 cases were sporadic and one case was inherited from the mother. Mutation analysis showed 13 out of 15 cases with the p.Gly380Arg mutation in the FGFR3 gene. Hydrocephalus was developed in three cases, required shunting in two cases.

Advantages and Disadvantages of Different Treatment Methods in Achondroplasia: A Review

Achondroplasia (ACH) is a disease caused by a missense mutation in the FGFR3 (fibroblast growth factor receptor 3) gene, which is the most common cause of short stature in humans. The treatment of ACH is necessary and urgent because untreated achondroplasia has many complications, both orthopedic and neurological, which ultimately lead to disability. This review presents the current and potential pharmacological treatments for achondroplasia, highlighting the advantages and disadvantages of all the drugs that have been demonstrated in human and animal studies in different stages of clinical trials. The article includes the potential impacts of drugs on achondroplasia symptoms other than short stature, including their effects on spinal canal stenosis, the narrowing of the foramen magnum and the proportionality of body structure. Addressing these effects could significantly improve the quality of life of patients, possibly reducing the frequency and necessity of hospitalization and painful surgical procedures, which are currently the only therapeutic options used. The criteria for a good drug for achondroplasia are best met by recombinant human growth hormone at present and will potentially be met by vosoritide in the future, while the rest of the drugs are in the early stages of clinical trials.

Should we be measuring DNA damage in human spermatozoa? New light on an old question

Assessments of sperm DNA damage are controversial because of perceived uncertainties over the relationship with pregnancy and the limited range of therapies available should positive results be returned. In this article, we highlight recent data supporting a chain of associations between oxidative stress in the male germ line, DNA damage in spermatozoa, defective DNA repair in the oocyte, the mutational load carried by the resulting embryo and the long-term health trajectory of the offspring. Any condition capable of generating oxidative damage in spermatozoa (age, obesity, smoking, prolonged abstinence, varicocele, chemical exposures, radiation etc.) is capable of influencing offspring health in this manner, creating a range of pathologies in the progeny including neuropsychiatric disorders and cancer. If sperm DNA damage is detected, there are several therapeutic interventions that can be introduced to improve DNA quality prior to the use of these cells in ART. We therefore argue that infertility specialists should be engaged in the diagnosis and remediation of sperm DNA damage as a matter of best practice, in order to minimize the risk of adverse health outcomes in children conceived using ART.

Pubertal growth in height, sitting height and leg length in achondroplasia

Background: Children with achondroplasia (ACH) appear to lack a pubertal growth spurt in height.Aim To explore the growth spurt in height and its segments sitting height and leg length, in a large sample of ACH cases using growth curve modelling.Subjects and methods: Height and sitting height were measured longitudinally in ACH children, and the data were analysed using the SITAR (SuperImposition by Translation and Rotation) growth model, which estimates a mean growth curve and random effects for individuals defining differences in size, pubertal timing and intensity.Results: Out of 402 ACH children, 85 boys and 75 girls aged 7-20 years had respectively 529 and 454 measurements of height and sitting height, with leg length calculated by difference. SITAR analysis identified peaks in mean height velocity at 13.3 and 11.3 years in boys and girls, with peak velocities of 4.3 and 4.4 cm/year. Mean peak velocity for sitting height was 3.0 cm/year, but leg length showed no peak. The SITAR models explained 92% to 99% of the cross-sectional variance.Conclusion: ACH children do experience a growth spurt in puberty, but only half that of control children. The spurt is due entirely to sitting height, with no leg length spurt.

Childhood prevalence of achondroplasia in New South Wales and the Australian Capital Territory, Australia

The aim of this study was to estimate the childhood prevalence of achondroplasia, trends over time in birth prevalence, and age at diagnosis in Australia. Children born between 1990 and 2019 with a clinical and radiological and/or molecular diagnosis of achondroplasia were identified from a tertiary hospital servicing New South Wales (NSW) and the Australian Capital Territory (ACT) and compared with population data from the Australian Bureau of Statistics. Childhood prevalence of achondroplasia, based on children ≤19 years of age and resident in NSW/ACT on June 30, 2019 (n = 109), was 5.2 per 100,000. A total of 127 individuals with achondroplasia were born in 1990-2019 in NSW/ACT. Birth prevalence rates increased across birth decades, from 3.3 per 100,000 live births in 1990-1999 to 5.3 per 100,000 in 2010-2019 (p < 0.0001). Median age at diagnosis decreased to 17 days in 2010-2019 compared with 30 days in 1990-1999 (p = 0.035), although the overall decreasing trend across consecutive decades did not reach statistical significance. This is the first study to show a rising birth prevalence rate for achondroplasia in Australia with a concurrent decreasing age at diagnosis, both of which were statistically significant after 2 decades.

Birth prevalence of achondroplasia: A systematic literature review and meta-analysis

Achondroplasia is a genetic disorder that results in disproportionate short stature. The true prevalence of achondroplasia is unknown as estimates vary widely. This systematic literature review and meta‐analysis was conducted to better estimate worldwide achondroplasia birth prevalence. PubMed, Embase, Scielo, and Google Scholar were searched, complemented by manual searching, for peer‐reviewed articles published between 1950 and 2019. Eligible articles were identified by two independent researchers using predefined selection criteria. Birth prevalence estimates were extracted for analysis, and the quality of evidence was assessed. A meta‐analysis using a quality effects approach based on the inverse variance fixed effect model was conducted. The search identified 955 unique articles, of which 52 were eligible and included. Based on the meta‐analysis, the worldwide birth prevalence of achondroplasia was estimated to be 4.6 per 100,000. Substantial regional variation was observed with a considerably higher birth prevalence reported in North Africa and the Middle East compared to other regions, particularly Europe and the Americas. Higher birth prevalence was also reported in specialized care settings. Significant heterogeneity (Higgins I² of 84.3) was present and some indication of publication bias was detected, based on visual asymmetry of the Doi plot with a Furuya‐Kanamori index of 2.73. Analysis of pooled data from the current literature yields a worldwide achondroplasia birth prevalence of approximately 4.6 per 100,000, with considerable regional variation. Careful interpretation of these findings is advised as included studies are of broadly varying methodological quality.