Lifetime impact of achondroplasia: Current evidence and perspectives on the natural history

International consensus guidelines on the implementation and monitoring of vosoritide therapy in individuals with achondroplasia

Achondroplasia is the most common genetic form of short-limbed skeletal dysplasia (dwarfism). Clinical manifestations and complications can affect individuals across the lifespan, including the need for adaptations for activities of daily living, which can affect quality of life. Current international guidelines focus on symptomatic management, with little discussion regarding potential medication, as therapeutic options were limited at the time of their publication. Vosoritide is the first pharmacological, precision treatment for achondroplasia; it was approved for use in 2021, creating a need for vosoritide treatment guidelines to support clinicians. An international collaborative of leading experts and patient advocates was formed to develop this Consensus Statement. The group developed the guideline scope and topics during a hybrid meeting in November 2023; guideline statements were subsequently ratified via Delphi methodology using a predefined consensus threshold. These statements provide recommendations across the treatment pathway, from starting treatment with vosoritide through ongoing monitoring and evaluation, to stopping vosoritide and ongoing monitoring following cessation. These guidelines recommend a minimum set of requirements and a practical framework for professionals and health services worldwide regarding the use of vosoritide to treat infants, children and young people with achondroplasia. This Consensus Statement is a supplement to already established consensus guidelines for management and care of individuals with achondroplasia.

Sustained growth-promoting effects of vosoritide in children with achondroplasia from an ongoing phase 3 extension study

BACKGROUND

Vosoritide is a C-type natriuretic peptide analog that addresses an underlying pathway causing reduced bone growth in achondroplasia. Understanding the vosoritide treatment effect requires evaluation over an extended duration and comparison with outcomes in untreated children.

METHODS

After completing ≥6 months of a baseline observational growth study and 52 weeks in a double-blind, placebo-controlled study (ClinicalTrials.gov: NCT03197766), participants were eligible to continue treatment in an open-label extension (ClinicalTrials.gov: NCT03424018) wherein all received 15 μg/kg vosoritide daily. Data from the CLARITY achondroplasia study provided an external untreated control population and reference data.

FINDINGS

The population comprised 119 participants. Annualized growth velocity with vosoritide was similar to the average-stature population before puberty. The mean (SD) differences in annualized growth velocity across each integer age (6-16 years) between treated and untreated children were 1.84 (0.38) cm/year in boys and 1.44 (0.63) cm/year in girls. Three-year comparisons of treated versus untreated children demonstrated an additional height gain of 5.75 cm (95% confidence interval [CI]: 4.93, 6.57) with vosoritide. A significant improvement in upper-to-lower body segment ratio at 3 years of treatment was observed for participants with assessments at age <11 (females) and <12 years (males) versus population-level, age-matched, untreated controls (p = 0.0087). The arm span-to-standing height ratio remained consistent with untreated participants. Vosoritide had a favorable safety profile with continuous treatment for up to 6 years (464.05 person years of exposure). No long-term harms or deaths were observed.

CONCLUSIONS

Vosoritide treatment was well tolerated and had sustained growth-promoting effects in children with achondroplasia treated for up to 6 years.

FUNDING

This work was funded by BioMarin Pharmaceutical.

Persistent growth-promoting effects of vosoritide in children with achondroplasia are accompanied by improvements in physical and social aspects of health-related quality of life

PURPOSE

Evaluate the impact of vosoritide on health-related quality of life in children with achondroplasia.

METHODS

Participants received vosoritide (15 μg/kg/day) in an extension trial (NCT03424018) after having participated in a placebo-controlled trial (NCT03197766).

RESULTS

The population comprised 119 participants (mean [SD] age 9.7 [2.6] years). Mean treatment duration was 4 (0.78) years. At year 3, the largest mean (SD) changes were observed in the Quality of Life of Short Stature Youth physical score (5.99 [19.41], caregiver reported; 6.32 [20.15], self-reported) and social score (2.85 [8.29] and 6.76 [22.64], respectively). Changes were greatest in participants with ≥1 SD increase in height z-score (physical: 11.36 [19.51], caregiver-reported [n = 38]; 8.48 [21.83], self-reported [n = 28]) (social: 5.84 [15.45] and 9.79 [22.80], respectively). To determine how domain scores may change with age in untreated persons, models were produced using observational/untreated-person data. A 1-year increase in age was associated with a change of 0.16 (SE, 0.55) and 0.16 (0.50), for caregiver-reported physical and social domain scores, respectively. Self-reported scores changed by 1.45 (0.71) and 1.92 (0.77), respectively.

CONCLUSION

These data suggest that after 3 years of treatment, vosoritide demonstrates a positive effect on physical and social functioning among children with achondroplasia, particularly in children with a more pronounced change in height z-score.

Feasibility study of the psychosocial effects of an online mindfulness intervention in children and adolescents with achondroplasia and their parents

INTRODUCTION

Achondroplasia is a common skeletal dysplasia caused by a mutation in the FGFR3 gene, leading to disproportionate short stature and various clinical features. Despite the absence of definitive pharmacological treatments, mindfulness-based interventions may offer psychosocial benefits for affected individuals and their families.

OBJECTIVES

This study aimed to assess the feasibility and psychosocial effects of an online mindfulness intervention for children and adolescents with achondroplasia and their parents.

METHODOLOGY

The intervention was an eight-week, synchronous online program with 15 participants: seven children and adolescents with achondroplasia and eight parents. Quantitative outcomes were assessed pre-and post-intervention using the State-Trait Anxiety Inventory for Children (STAIC) and the Multifactorial Self-Assessment Child Adaptation Test (TAMAI) for the younger participants, along with the Brief Symptom Inventory (BSI-18) for parents. Participant satisfaction was assessed using a customized survey, and qualitative data were collected through semi-structured interviews.

RESULTS

The study demonstrated high feasibility, with 84.61% adherence and 93.75% participant satisfaction. Average anxiety levels decreased in children and adolescents (30.60 ± 5.12 to 26.80 ± 6.94, p = .285) and parents (3.67 ± 3.98 to 1.00 ± .89, p = .066). Emotional regulation was the most reported improvement category by children and adolescents (31.4%), while general well-being was the most noted by parents (29.63%).

CONCLUSIONS

The results support the feasibility of this online mindfulness intervention for individuals with achondroplasia and their parents, indicating benefits for psychosocial well-being. Future studies should address these limitations by expanding sample sizes, exploring hybrid intervention models, and ensuring data anonymity. Integrating mindfulness into comprehensive psychosocial care strategies could enhance the quality of life for these populations.

[Achondroplasia : New era of orthopedic treatment?]

Achondroplasia is the most common skeletal dysplasia. With the development of new growth-promoting drug treatment for children and adolescents with achondroplasia, multidisciplinary care has become increasingly more important. In addition to orthopedic care, a specialized team comprised of pediatrics/endocrinology, radiology, neurosurgery, otorhinolaryngology, anesthesiology, physiotherapy, psychology and other disciplines is necessary to develop and implement a holistic concept to improve the quality of life for individuals affected by achondroplasia. The orthopedic management of achondroplasia has become even more complex and multidisciplinary due to these new medical and surgical developments. These new developments herald a new era of orthopedic and multidisciplinary care for achondroplasia.

Quality of Life in Short Stature Children With Skeletal Dysplasia: A Cross Sectional Study Using the Quality of Life in Short Stature Youth Questionnaire

Patients with skeletal dysplasia, including achondroplasia (ACH) and osteogenesis imperfecta (OI), exhibit a variety of short stature, which affect various aspects of their quality of life (QoL). The QoL of adult patients with skeletal dysplasia have been reported; however, research on QoL in children remains limited. The QoL in Short Stature Youth (QoLISSY) is a QoL survey tool developed specifically for short stature children and adolescent. We assessed the QoLISSY scores in children with various skeletal dysplasias presenting with short stature and compared the scores among ACH, OI, and other dysplasias. Forty and 72 questionnaires were sent to the children with various skeletal dysplasias and their parents, respectively, and 24 and 54 valid questionnaires, respectively, were collected. There were no significant differences in age, sex, or height between the patients with ACH, OI, and other skeletal dysplasias. Parents' social, emotional, and total QoL scores were significantly lower in the ACH group than in the OI group. A sub-analysis revealed that the height standard deviation score did not correlate with the QoLISSY scores in all groups except for the belief score of OI parents.

Natural history of spinal cord compression stage AFMS3 in infants with achondroplasia: retrospective cohort study

BACKGROUND AND OBJECTIVE

Foramen magnum stenosis (FMS) is a common, serious complication of achondroplasia in infancy and associated with sudden infant death. The Achondroplasia Foramen Magnum Score (AFMS; 0-4) is used to classify the severity of stenosis to inform appropriate neurosurgical management. Infants with AFMS4 are referred for neurosurgery, while well children with AFMS3 undergo repeat MRI routinely after 12 months.As the natural history of children with AFMS3 is currently unclear, the objective was to review follow-up MRI scans of infants initially classified as AFMS3 to define more clearly the evolution of this degree of stenosis.

DESIGN

This retrospective cohort study, from two tertiary centres, included infants with a confirmed diagnosis of achondroplasia and AFMS3 on initial MRI who subsequently underwent repeat MRI or proceeded straight to neurosurgery.

RESULTS

Twenty-two cases satisfied the inclusion criteria. Mean age in months was 6.23 (SD±3.82) and 17.95 (SD±7.68) at baseline and follow-up scans, respectively. Follow-up MRI showed no change in 23% (N=5), improvement in 36% (N=8) to either AFMS1 (N=5) or AFMS2 (N=3). There was progression in 41% to AFMS4 (N=8). One case had neurosurgey without follow-up MRI (N=1).

CONCLUSIONS

These results support MRI screening for FMS in infants with achondroplasia. Furthermore, infants with AFMS3 should undergo follow-up MRI as over 40% progress prompting neurosurgical intervention. There is currently no consensus on frequency or timing of screening for AFMS3 in achondroplasia; however, we suggest that guidance for follow-up imaging is modified to 6 months to detect progression earlier in this at-risk cohort.

Anatomical Characteristics of Cervicomedullary Compression on MRI Scans in Children with Achondroplasia

This retrospective study assessed anatomical characteristics of cervicomedullary compression in children with achondroplasia. Twelve anatomical parameters were analyzed (foramen magnum diameter and area; myelon area; clivus length; tentorium and occipital angles; brainstem volume outside the posterior fossa; and posterior fossa, cerebellum, supratentorial ventricular system, intracranial cerebrospinal fluid, and fourth ventricle volumes) from sagittal and transversal T1- and T2-weighted magnetic resonance imaging (MRI) scans from 37 children with achondroplasia aged ≤ 4 years (median [range] 0.8 [0.1-3.6] years) and compared with scans from 37 children without achondroplasia (median age 1.5 [0-3.9] years). Mann-Whitney U testing was used for between-group comparisons. Foramen magnum diameter and area were significantly smaller in children with achondroplasia compared with the reference group (mean 10.0 vs. 16.1 mm [p < 0.001] and 109.0 vs. 160.8 mm2 [p = 0.005], respectively). The tentorial angle was also steeper in children with achondroplasia (mean 47.6 vs. 38.1 degrees; p < 0.001), while the clivus was significantly shorter (mean 23.5 vs. 30.3 mm; p < 0.001). Significant differences were also observed in myelon area, occipital angle, fourth ventricle, intracranial cerebrospinal fluid and supratentorial ventricular volumes, and the volume of brainstem protruding beyond the posterior fossa (all p < 0.05). MRI analysis of brain structures may provide a standardized value to indicate decompression surgery in children with achondroplasia.

Challenges to self-care and domestic life for adults with disproportionate short statured skeletal dysplasia: a mixed method systematic review

PURPOSE

This review aims to assess the impact of pain and limitations across self-care and domestic tasks among adults with disproportionate short statured skeletal dysplasia (SD).

METHODS

A systematic search was conducted across six electronic databases without language or year of publication restrictions from the date of inception of each database through to 31 July 2024. Clear inclusion criteria were established before search initiation and quality assessment was performed using the Mixed Methods Appraisal Tool (MMAT).

RESULTS

Eight studies including 1,114 adults (mean age 33.1 years) met the inclusion criteria, demonstrating high methodological quality (MMAT ranging from 80 to 100%). Challenges in self-care and domestic tasks were prevalent among adults with disproportionate short statured SD. Personal hygiene (65.6%, 95% confidence interval (95%CI): 55.3-74.6%), donning/doffing shoes (54.3%, 95%CI: 38.2-70.0%), and reaching objects (20.2%, 95%CI: 16.8-24.1%) were the most prevalent difficulties, generally falling within low-moderate difficulty. Studies consistently identified mild-intensity pain adversely affected adult's abilities to complete daily activities. Due to the significant heterogeneity of included studies, a meta-analysis was not conducted.

CONCLUSIONS

Adults with disproportionate short statured SD experience challenges in self-care and domestic tasks, alongside a notable trend that suggests a higher prevalence of pain is linked to increased difficulty in completing daily tasks.

Progress in managing children with achondroplasia

INTRODUCTION

Achondroplasia is a heritable disorder of the skeleton that affects approximately 300,000 individuals worldwide. Until recently, treatment for this condition has been purely symptomatic. Efficacious treatment options for children are now approved or are in clinical trials.

AREAS COVERED

This review discusses key advances in the therapeutic management of children with achondroplasia, including vosoritide, the first approved drug, and other emerging precision therapies. These include navepegritide, a long-acting form of C-type natriuretic peptide, and infigratinib, a tyrosine kinase receptor inhibitor, summarizing trial outcomes to date.

EXPERT OPINION

The advent of the first approved precision therapy for achondroplasia in vosoritide has been a paradigm shifting advance for children affected by this condition. In addition to changing their natural growth history, it is hoped that it will decrease their medical complications and enhance functionality. These new treatment options highlight the importance of prompt prenatal identification and subsequent testing of a suspected fetus with achondroplasia and counseling of families. It is hoped that, in the near future, families will have the option to consider a range of effective targeted therapies that best suit their child with achondroplasia, starting from birth should they choose.

Patients with achondroplasia have increased risk of 90-day adverse events following laminectomy: A matched comparison using a national database

PURPOSE

Performing laminectomies in patients with achondroplasia-a common skeletal dysplasia-can present unique challenges. There are a limited number of studies that have reported on the adverse effects of laminectomies in patients with achondroplasia. To compare the 90-day postoperative adverse events following laminectomy in patients with and without achondroplasia.

METHODS

Retrospective cohort study using the 2010-2020 PearlDiver Mariner 91 administrative database was used to identify patients who underwent thoracic, thoracolumbar, or lumbar laminectomy. Patients with achondroplasia were matched 1:4 to patients without achondroplasia based on age, sex, insurance, and ECI. Univariate and multivariate logistic regression analyses assessed and compared 90-day adverse events. Odds ratios (OR), 95% confidence intervals (CI), and p-values were reported with significance set at p < 0.05.

RESULTS

A multivariate analysis revealed that when laminectomy was performed, patients with achondroplasia were 2.82 times more likely to have 90-day AE compared to those without achondroplasia (p < 0.001). When comparing individual subtypes of adverse events, patients with achondroplasia were found to have significantly greater odds of a transfusion (OR 6.40, p < 0.001), UTI (OR 3.79, p < 0.001), disruption of wound (OR 3.71, p < 0.001), and hematoma (OR 2.94, p = 0.032). Pneumonia, cardiac arrest, AKI, other perioperative events, durotomy, and VTE were not significantly different between the two cohorts.

CONCLUSION

This study uses one of the largest cohorts to compare patients with and without achondroplasia undergoing laminectomy. Patients with achondroplasia were found to have a significantly greater risk of 90-day adverse events following laminectomy compared to their matched cohort of patients without achondroplasia.

Achondroplasia current concept of orthopaedic management

Achondroplasia, the most common form of inherited disproportionate short stature, is caused by mutations in the fibroblast growth factor receptor 3 gene. The typical clinical features of achondroplasia include short stature, rhizomelic disproportion, joint hyperlaxity, spinal deformity and deformity of the upper and lower limbs. The latter are among the challenges of state-of-the-art orthopaedic treatment plans and significantly contribute to the burden of the disease in individuals with achondroplasia. Multidisciplinary preoperative individual decision-making concerning surgical interventions should be considered. New medical treatments for achondroplasia have been developed and (some) have been approved for clinical use in several countries. While the number of research articles on achondroplasia is increasing rapidly, many unknown or controversial orthopaedic topics remain. Furthermore, in view of new medical developments with improvements in growth and potentially other effects, the timing and algorithms of orthopaedic treatments (e.g. guided growth, limb lengthening and deformity correction) need to be re-evaluated. While standing height is the primary research focus in medical therapy, it is crucial to comprehensively assess orthopaedic parameters in this multifactorial disease. The current treatment of patients with achondroplasia requires specialised multidisciplinary centres with transitional care and individual orthopaedic counselling.

Low-dose infigratinib increases bone growth and corrects growth plate abnormalities in an achondroplasia mouse model

Achondroplasia (ACH), the most common form of disproportionate short stature, is caused by gain-of-function point mutations in fibroblast growth factor receptor 3 (FGFR3). Abnormally elevated activation of FGFR3 modulates chondrocyte proliferation and differentiation via multiple signaling pathways, such as the MAPK pathway. Using a mouse model mimicking ACH (Fgfr3Y367C/+), we have previously shown that daily treatment with infigratinib (BGJ398), a selective and orally bioavailable FGFR1-3 inhibitor, at a dose of 2 mg/kg, significantly increased bone growth. In this study, we investigated the activity of infigratinib administered at substantially lower doses (0.2 and 0.5 mg/kg, given once daily) and using an intermittent dosing regimen (1 mg/kg every 3 days). Following a 15-day treatment period, these low dosages were sufficient to observe significant improvement of clinical hallmarks of ACH such as growth of the axial and appendicular skeleton and skull development. Immunohistological labeling demonstrated the positive impact of infigratinib on chondrocyte differentiation in the cartilage growth plate and the cartilage end plate of the vertebrae. Macroscopic and microcomputed analyses showed enlargement of the foramen magnum area at the skull base, thus improving foramen magnum stenosis, a well-recognized complication in ACH. No changes in FGF23 or phosphorus levels were observed, indicating that the treatment did not modify phosphate homeostasis. This proof-of-concept study demonstrates that infigratinib administered at low doses has the potential to be a safe and effective therapeutic option for children with ACH.

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.

Evaluation of functionality-mobility in patients with skeletal dysplasias. Application of the STEMS tool ("everyday symptoms and mobility screening tool for skeletal dysplasias")

Individuals with differing forms of skeletal dysplasias (SD) frequently report impaired mobility and symptoms. With the objetive to evaluate mobility and associated symptoms in people with SD at an Argentinian pediatric hospital, using an Argentinian version of the Screening Tool for Everyday Mobility and Symptoms (STEMS), a simple questionnaire that allows clinicians to quickly identify the presence of symptoms associated with mobility in people with SD, while considering different environmental settings and the use of assistive devices, an analytical study of a consecutive sample of patients older than 5 years with SD and their affected relatives was carried out.Diagnosis, comorbidities, socioenvironmental, therapeutic, auxological and mobility variables were recorded. The presence and intensity of symptoms was noted through use of both the STEMS and validated scales. Descriptive, association and correlation analyzes were performed. One hundred and nineteen individuals with SD were enrolled in the study and divided into groups: Osteogenesis Imperfecta (OI, n = 55), Achondroplasia (ACH, n = 36) and Other SD resulting in disproportionate short stature (n = 28). Mobility assistive devices were almost exclusively used by individuals with OI. They were more frequently used by individuals with overweight and obesity, more severe form of the disease and in the outdoor settings. Two thirds (66.4%) of the individuals assessed in this study reported pain, 87.4% reported fatigue, and 58.8% reported both pain and fatigue. The intensity of symptoms was similar between groups and correlated with age and auxological variables. The STEMS was clear, easy and quick to use for identifying presence of pain and fatigue in this population group. The STEMS proved to be a simple and useful tool for evaluating functional mobility and associated symptoms in our population of individuals with SD.

What Is the Role for Pediatric Endocrinologists in the Management of Skeletal Dysplasias?

Children with skeletal dysplasias have not been consistently managed by pediatric endocrinologists despite the recognized expertise of these practitioners in managing genetic growth disorders. Growth-altering treatments have broadened the role of the pediatric endocrinologist to manage and sometimes become primary coordinators for genetic disorders such as Turner syndrome and Prader-Willi syndrome. We illustrate how recent advances in understanding the pathophysiology of skeletal disorders and the development of targeted treatments provide an opportunity for pediatric endocrinologists to further expand their role in managing certain skeletal dysplasias, including achondroplasia.

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.

New treatments for children with achondroplasia

Achondroplasia is the most common form of dwarfism in humans, caused by a common pathogenic variant in the gene encoding fibroblast growth factor receptor 3, FGFR3, which impairs the process of endochondral ossification of the growing skeleton. In this Review, we outline the clinical and genetic hallmarks of achondroplasia and related FGFR3 conditions, the natural history and impact of achondroplasia over a patient's lifespan, and diagnosis and management options. We then focus on the new and emerging drug therapies that target the underlying pathogenesis of this condition. These new options are changing the natural growth patterns of achondroplasia, with the prospect of better long-term health outcomes for patients.

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.

Vosoritide therapy in children with achondroplasia aged 3-59 months: a multinational, randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Vosoritide is a recombinant C-type natriuretic peptide analogue that increases annualised growth velocity in children with achondroplasia aged 5-18 years. We aimed to assess the safety and efficacy of vosoritide in infants and children younger than 5 years.

METHODS

This double-blind, randomised, placebo-controlled, phase 2 trial was done in 16 hospitals across Australia, Japan, the UK, and the USA. Children younger than 60 months with a clinical diagnosis of achondroplasia confirmed by genetic testing and who had completed a baseline growth study or observation period were enrolled into one of three sequential cohorts based on age at screening: 24-59 months (cohort 1); 6-23 months (cohort 2); and 0-5 months (cohort 3). Each cohort included sentinels who received vosoritide to determine appropriate daily drug dose, with the remainder randomly assigned (1:1) within each age stratum (except in Japan, where participants were randomly assigned within each cohort) to receive daily subcutaneous injections of vosoritide (30·0 μg/kg for infants aged 0-23 months; 15·0 μg/kg for children aged 24-59 months) or placebo for 52 weeks. Participants, caregivers, investigators, and the sponsor were masked to treatment assignment. The first primary outcome was safety and tolerability, assessed in all participants who received at least one study dose. The second primary outcome was change in height Z score at 52 weeks from baseline, analysed in all randomly assigned participants. This trial is registered with EudraCT, 2016-003826-18, and ClinicalTrials.gov, NCT03583697.

FINDINGS

Between May 13, 2018, and March 1, 2021, 75 participants were recruited (37 [49%] females). 11 were assigned as sentinels, whereas 32 were randomly assigned to receive vosoritide and 32 placebo. Two participants discontinued treatment and the study: one in the vosoritide group (death) and one in the placebo group (withdrawal). Adverse events occurred in all 75 (100%) participants (annual rate 204·5 adverse events per patient in the vosoritide group and 73·6 per patient in the placebo group), most of which were transient injection-site reactions and injection-site erythema. Serious adverse events occurred in three (7%) participants in the vosoritide group (decreased oxygen saturation, respiratory syncytial virus bronchiolitis and sudden infant death syndrome, and pneumonia) and six (19%) participants in the placebo group (petit mal epilepsy, autism, gastroenteritis, vomiting and parainfluenza virus infection, respiratory distress, and skull fracture and otitis media). The least-squares mean difference for change from baseline in height Z score between the vosoritide and placebo groups was 0·25 (95% CI -0·02 to 0·53).

INTERPRETATION

Children with achondroplasia aged 3-59 months receiving vosoritide for 52 weeks had a mild adverse event profile and gain in the change in height Z score from baseline.

FUNDING

BioMarin Pharmaceutical.

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.

Lifetime Impact Study for Achondroplasia (LISA): Findings from an observational and multinational study focused on health-related quality of life in individuals with achondroplasia in Latin America

Purpose

The multisystem clinical manifestations and complications of achondroplasia, the most common form of disproportionate short stature, can cause functional impairment and psychosocial burden. The Lifetime Impact Study for Achondroplasia (LISA), aimed to assess health-related quality of life and medical resource utilization among Latin America patients with achondroplasia.

Methods

Data were collected from individuals aged 3 years and above in Argentina, Brazil, and Colombia between 2018 and 2021. A total of 172 patients participated in the study.

Results

Children with achondroplasia reported lower scores compared with average stature children in Quality of Life in Short Stature Youth (QoLISSY) and Pediatric Quality of Life Inventory (PedsQL) questionnaires, with the greatest impact on physical and social domains. Among adolescents, a significant percentage reported pain, 10.3% experienced pain in 3 or more sites. Adults scored lower than the reference population in the EQ-5D-5L Visual Analog Score, and a considerable portion reported moderate to severe anxiety/depression, pain or discomfort, and mobility problems. The Nottingham Health Profile (NHP) revealed poor health status in terms of energy, pain, and mobility. Medical events, particularly musculoskeletal and connective tissue disorders were reported, resulting in high medical resource utilization.

Conclusion

Overall, the Lifetime Impact Study for Achondroplasia study provides extensive data on health-related quality of life, psychosocial impact, and health care resource utilization among individuals with achondroplasia in Latin America. The findings confirm a significant burden of illness across multiple domains for these individuals.

Once-weekly TransCon CNP (navepegritide) in children with achondroplasia (ACcomplisH): a phase 2, multicentre, randomised, double-blind, placebo-controlled, dose-escalation trial

Background

TransCon CNP (navepegritide) is an investigational prodrug of C-type natriuretic peptide (CNP) designed to allow for continuous CNP exposure with once-weekly dosing. This 52-week phase 2 (ACcomplisH) trial assessed the safety and efficacy of TransCon CNP in children with achondroplasia.

Methods

ACcomplisH is a global, randomised, double-blind, placebo-controlled, dose-escalation trial. Study participants were recruited between June 10, 2020, and September 24, 2021. Eligible participants were prepubertal, aged 2-10 years, with genetically confirmed achondroplasia, and randomised 3:1 to once-weekly subcutaneous injections of TransCon CNP (6, 20, 50, or 100 μg CNP/kg/week) or placebo for 52 weeks. Primary objectives were safety and annualised growth velocity (AGV). ACcomplisH is registered with ClinicalTrials.gov (NCT04085523) and Eudra (CT 2019-002754-22).

Findings

Forty-two participants received TransCon CNP at doses of 6 μg (n = 10; 7 female), 20 μg (n = 11; 3 female), 50 μg (n = 10; 3 female), or 100 μg (n = 11; 6 female) CNP/kg/week, with 15 receiving placebo (5 female). Treatment-emergent adverse events (TEAEs) were mild or moderate with no grade 3/4 events reported. There were 2 serious TEAEs that were assessed as not related to TransCon CNP. Eleven injection site reactions occurred in 8 participants receiving TransCon CNP and no symptomatic hypotension occurred. TransCon CNP demonstrated a dose-dependent improvement in AGV. At 52 weeks, TransCon CNP 100 μg CNP/kg/week significantly improved AGV vs placebo (least squares mean [95% CI] 5.42 [4.74-6.11] vs 4.35 [3.75-4.94] cm/year; p = 0.0218), and improved achondroplasia-specific height SDS from baseline (least squares mean [95% CI] 0.22 [0.02-0·41] vs -0·08 [-0.25 to 0.10]; p = 0.0283). All participants completed the randomised period and continued in the ongoing open-label extension period receiving TransCon CNP 100 μg CNP/kg/week.

Interpretation

This phase 2 trial suggests that TransCon CNP is effective, safe, with low injection site reaction frequency, and may provide a novel, once-weekly treatment option for children with achondroplasia. These results support TransCon CNP at 100 μg CNP/kg/week in the ongoing pivotal trial.

Funding

Ascendis Pharma, A/S.

Growth patterns of young achondroplasia patients in Korea and predictability of neurosurgical procedures

BACKGROUND

Achondroplasia is an autosomal dominant disorder mainly affecting bony growth, typically resulting in markedly short stature. From a neurosurgical viewpoint, patients sometimes develop spinal cord compression at the narrowed foramen magnum and hydrocephalus. This study aims to construct growth references for height, weight, and head circumference (HC) of young achondroplasia patients in Korea and to evaluate the predictability of the necessity and timing of neurosurgical procedures through growth patterns.

METHODS

Growth data were collected from achondroplasia patients who visited our institution between January 2002 and August 2022. First, we constructed percentile growth curves of height, weight, and HC for the patients under 3 years of age with the generalized additive model for location, scale, and shape (GAMLSS). Second, the growth patterns of the patients with hydrocephalus who underwent neurosurgical procedures such as foramen magnum decompression (FMD) and ventriculoperitoneal (VP) shunt were analyzed.

RESULTS

There were 125 achondroplasia patients, including 67 males and 58 females. Among 125 patients, 46 underwent FMD, and 5 underwent VP shunt. As short stature and macrocephaly were typical characteristics of achondroplasia, the height of achondroplasia was lower than that of the general population, and HC in achondroplasia showed accelerated growth postnatally. There were no significant changes in HC in hydrocephalus patients before they underwent neurosurgical procedures. The influence of hydrocephalus on the growth patterns of HC in achondroplasia seemed insignificant.

CONCLUSION

Growth references for height, weight, and HC in young achondroplasia patients were constructed. It is the first report of growth patterns of achondroplasia in Korea. Unlike other pediatric patients, the diagnosis of hydrocephalus and the necessity of neurosurgical procedures are hard to be predicted with HC in achondroplasia. Neuroimaging should be considered for achondroplasia patients with neurological symptoms.

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.

European Achondroplasia Forum guiding principles for the detection and management of foramen magnum stenosis

Foramen magnum stenosis is a serious, and potentially life-threatening complication of achondroplasia. The foramen magnum is smaller in infants with achondroplasia, compared with the general population, and both restricted growth in the first 2 years and premature closure of skull plate synchondroses can contribute to narrowing. Narrowing of the foramen magnum can lead to compression of the brainstem and spinal cord, and result in sleep apnoea and sudden death. There is a lack of clarity in the literature on the timing of regular monitoring for foramen magnum stenosis, which assessments should be carried out and when regular screening should be ceased. The European Achondroplasia Forum (EAF) is a group of clinicians and patient advocates, representative of the achondroplasia community. Members of the EAF Steering Committee were invited to submit suggestions for guiding principles for the detection and management of foramen magnum stenosis, which were collated and discussed at an open workshop. Each principle was scrutinised for content and wording, and anonymous voting held to pass the principle and vote on the level of agreement. A total of six guiding principles were developed which incorporate routine clinical monitoring of infants and young children, timing of routine MRI screening, referral of suspected foramen magnum stenosis to a neurosurgeon, the combination of assessments to inform the decision to decompress the foramen magnum, joint decision making to proceed with decompression, and management of older children in whom previously undetected foramen magnum stenosis is identified. All principles achieved the ≥ 75% majority needed to pass (range 89-100%), with high levels of agreement (range 7.6-8.9). By developing guiding principles for the detection and management of foramen magnum stenosis, the EAF aim to enable infants and young children to receive optimal monitoring for this potentially life-threatening complication.

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.

Parents' Experience of Administering Vosoritide: A Daily Injectable for Children with Achondroplasia

INTRODUCTION

Vosoritide is the first approved pharmacological treatment for achondroplasia and is indicated for at-home injectable administration by a trained caregiver. This research aimed to explore parents' and children's experience of initiating vosoritide and administering this treatment at home.

METHODS

Qualitative telephone interviews were conducted with parents of children being treated with vosoritide in France and Germany. Interviews were transcribed and analysed using thematic analysis.

RESULTS

Fifteen parents participated in telephone interviews in September and October 2022. The median age of children in this sample was 8 years old (range 3-13 years) and children had been taking treatment from 6 weeks to 13 months. Four themes document families' experience with vosoritide: (1) awareness of vosoritide treatment, uncovering that parents first heard of vosoritide through their own research, patient advocacy groups, or through their physicians; (2) treatment understanding and decision-making, which found that their decision to take treatment is based on a desire to relieve future medical complications and increase height for improved independence, and they consider the extent to which the treatment has severe side effects; (3) training and initiation, which showed that the hospital initiation and training sessions varied considerably both across and within countries, with different treatment centres taking different approaches; and (4) managing treatment at home brings psychological and practical challenges, which are ultimately overcome with perseverance and available support.

CONCLUSIONS

Parents and children are resilient to challenges posed by a daily injectable treatment and highly motivated to improve their quality of life. Parents are prepared to overcome short-term treatment challenges for future gains in terms of health and functional independence for their children. Greater support could ensure they have the right information to initiate treatment and manage treatment at home, which will improve parents' and children's experience.

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.

Meeting Report from 2nd ICCBH-ERN BOND Spinal Complications in Children and Adults with Achondroplasia Workshop, Dublin, Ireland, 2nd July 2022

A pre-meeting workshop on spinal complications in children and adults with achondroplasia was held in Dublin, Ireland at the 10th International Conference on Children's Bone Health (ICCBH) 2-5 July 2022. The pathophysiology, natural history and medical/surgical management of thoraco-lumbar kyphosis and spinal stenosis remains poorly described in the literature. The structure of the workshop consisted of lectures, a debate and an interactive round table discussion. In total over 100 delegates affiliated to over 70 institutions from 20 countries were in attendance.

Optimising care and follow-up of adults with achondroplasia

Background

Achondroplasia is a genetic condition that can cause complications across the lifespan. While complications in childhood are well documented, the natural history of achondroplasia in adults has, until recently, been relatively lacking, and little is known about the care they receive or how they access it. The European Achondroplasia Forum undertook two exploratory surveys, one for healthcare professionals (HCPs) and one for patient advocacy group (PAG) representatives, to gain an understanding of current practices of the transition process of individuals with achondroplasia from paediatric to adult services and how adults perceive their care.

Results

Most HCP respondents followed up more children than adults, and 8/15 responded that individuals did not transition to an adult multidisciplinary team (MDT) after paediatric care. Of 10 PAG respondents, none considered the experience of transition to adult services as good or very good and 50% considered it to be poor or very poor. A total of 64% (7/11) described the coordination of transition to adult services as “Not satisfactory” or “Poor”. HCPs and PAG representatives largely agreed on the core specialists involved in adult care (orthopaedic surgeons, physiotherapists, rehabilitation specialists, rheumatologists, clinical geneticists). However, there was a discrepancy in the understanding of healthcare needs outside of this, with PAG representatives selecting neurosurgeons and genetic counsellors, while HCPs selected pulmonologists and obstetricians/gynaecologists. There was agreement between HCP and PAG respondents on the key barriers to effective care of adults with achondroplasia, with lack of an adult MDT, lack of interest from individuals in accessing care, and less experience in adult than paediatric MDTs ranking highly.

Conclusions

This study indicates that the care and follow up of adults with achondroplasia is challenging. Individuals are often lost to, or decline, follow up as they leave paediatric care, and it is largely unknown how, where, and why adults with achondroplasia access care later in life. Lifelong, multidisciplinary specialist care led by an identified physician should be accessible to all individuals with achondroplasia. It is important to ensure barriers to optimal care are addressed to enable access to appropriate care for all individuals with achondroplasia.

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.

Literature review and expert opinion on the impact of achondroplasia on medical complications and health-related quality of life and expectations for long-term impact of vosoritide: a modified Delphi study

BACKGROUND

Achondroplasia is associated with disproportionate short stature and significant and potentially severe medical complications. Vosoritide is the first medicine to treat the underlying cause of achondroplasia and data from phase 3 and phase 2 extension studies showed effects on growth and body proportions. However, there are currently no long-term data available on the direct impact on endpoints such as medical complications and health-related quality of life (HRQoL). This study explored the perceived impact of achondroplasia on medical complications, HRQoL, healthcare resource use and mortality, and potential modifying effects of vosoritide, based on published evidence and expert opinion. Structured expert opinion was obtained by an international modified Delphi study among 14 experts in managing achondroplasia performed on a virtual platform and consisting of an explorative phase followed by an anonymous individual rating round.

RESULTS

Overall, the panelists expect that in individuals starting long-term treatment between 2 years of age and puberty, growth velocity increases observed in the clinical trials will be maintained until final height is reached (92% agreement) and will likely result in clinically meaningful improvements in upper-to-lower body segment ratio (85%). Earlier treatment initiation will likely result in a greater final height (100%) and more likely improve proportionality (92%) than later treatment. Although current data are limited, ≥ 75% of panelists find it conceivable that the earlier long-term treatment is started, the greater the probability of a positive effect on the lifetime incidence of symptomatic spinal stenosis, kyphosis, obstructive sleep apnea, and foramen magnum stenosis. These are among the most clinically important complications of achondroplasia because of their high impact on comorbidity, mortality, and/or HRQoL. A positive effect of vosoritide on the incidence of surgeries through lifetime was considered more likely with earlier long-term treatment (90%).

CONCLUSIONS

This explorative study, based on international expert opinion, provides further insight into the medical and functional impacts of achondroplasia and how these might be modified through long-term use of vosoritide. The results can be used to guide the direction and design of future research to validate the assumptions and to discuss potential treatment outcomes with disease modifying therapies with families and clinicians.

Key measurement concepts and appropriate clinical outcome assessments in pediatric achondroplasia clinical trials

BACKGROUND

This study aimed to identify fit-for-purpose clinical outcome assessments (COAs) to evaluate physical function, as well as social and emotional well-being in clinical trials enrolling a pediatric population with achondroplasia. Qualitative interviews lasting up to 90 min were conducted in the US with children/adolescents with achondroplasia and/or their caregivers. Interviews utilized concept elicitation methodology to explore experiences and priorities for treatment outcomes. Cognitive debriefing methodology explored relevance and understanding of selected COAs.

RESULTS

Interviews (N = 36) were conducted with caregivers of children age 0-2 years (n = 8) and 3-7 years (n = 7) and child/caregiver dyads with children age 8-11 years (n = 15) and 12-17 years (n = 6). Children/caregivers identified pain, short stature, impacts on physical functioning, and impacts on well-being (e.g. negative attention/comments) as key bothersome aspects of achondroplasia. Caregivers considered an increase in height (n = 9/14, 64%) and an improvement in limb proportion (n = 11/14, 71%) as successful treatment outcomes. The Childhood Health Assessment Questionnaire (CHAQ) and Quality of Life in Short Stature Youth (QoLISSY-Brief) were cognitively debriefed. CHAQ items evaluating activities, reaching, and hygiene were most relevant. QoLISSY-Brief items evaluating reaching, height bother, being treated differently, and height preventing doing things others could were most relevant. The CHAQ and QoLISSY-Brief instructions, item wording, response scales/options and recall period were well understood by caregivers and adolescents age 12-17. Some children aged 8-11 had difficulty reading, understanding, or required caregiver input. Feedback informed minor amendments to the CHAQ and the addition of a 7-day recall period to the QoLISSY-Brief. These amendments were subsequently reviewed and confirmed in N = 12 interviews with caregivers of children age 0-11 (n = 9) and adolescents age 12-17 (n = 3).

CONCLUSIONS

Achondroplasia impacts physical functioning and emotional/social well-being. An increase in height and improvement in limb proportion are considered to be important treatment outcomes, but children/adolescents and their caregivers expect that a successful treatment should also improve important functional outcomes such as reach. The CHAQ (adapted for achondroplasia) and QoLISSY-Brief are relevant and appropriate measures of physical function and emotional/social well-being for pediatric achondroplasia trials; patient-report is recommended for age 12-17 years and caregiver-report is recommended for age 0-11 years.

[Clinical features and FGFR3 mutations of children with achondroplasia]

OBJECTIVES

To study the clinical features and fibroblast growth factor receptor 3 (FGFR3) gene mutations of children with achondroplasia (ACH) through an analysis of 17 cases.

METHODS

A retrospective analysis was performed on the clinical data and FGFR3 gene detection results of 17 children with ACH who were diagnosed from January 2009 to October 2021.

RESULTS

Of the 17 children with ACH, common clinical manifestations included disproportionate short stature (100%, 17/17), macrocephaly (100%, 17/17), trident hand (82%, 14/17), and genu varum (88%, 15/17). The common imaging findings were rhizomelic shortening of the long bones (100%, 17/17) and narrowing of the lumbar intervertebral space (88%, 15/17). Major complications included skeletal dysplasia (100%, 17/17), middle ear dysfunction (82%, 14/17), motor/language developmental delay (88%, 15/17), chronic pain (59%, 10/17), sleep apnea (53%, 9/17), obesity (41%, 7/17), foramen magnum stenosis (35%, 6/17), and hydrocephalus (24%, 4/17). All 17 children (100%) had FGFR3 mutations, among whom 13 had c.1138G>A hotspot mutations of the FGFR3 gene, 2 had c.1138G>C mutations of the FGFR3 gene, and 2 had unreported mutations, with c.1252C>T mutations of the FGFR3 gene in one child and c.445+2_445+5delTAGG mutations of the FGFR3 gene in the other child.

CONCLUSIONS

This study identifies the unreported mutation sites of the FGFR3 gene, which extends the gene mutation spectrum of ACH. ACH is a progressive disease requiring lifelong management through multidisciplinary collaboration.

Physical Activity, Exercise, and Sports in Individuals with Skeletal Dysplasia: What Is Known about Their Benefits?

There is a lack of knowledge about the practice of physical activity, exercise, and sports in people with skeletal dysplasia (SD). This study aimed to characterize the physical fitness of people with SD; investigate the benefits of physical activity, exercise, or sports programs for people with SD; identify the adapted physical activities that can be prescribed to individuals with SD; and identify the most common and effective structural characteristics and guidelines for the evaluation of individuals with SD and corresponding activity prescriptions. Electronic searches were carried out in the PubMed, Scopus, SPORTDiscus, Psycinfo, and Web of Science databases in October 2021 and March 2022 and included papers published until 3 March 2022. The search strategy terms used were “dwarfism”, “dwarf”, “skeletal dysplasia”, “achondroplasia”, “pseudoachondroplasia”, “hypochondroplasia”, “campomelic dysplasia”, “hair cartilage hypoplasia”, “x-linked hypophosphatemia”, “metaphyseal chondrodysplasia schmid type”, “multiple epiphyseal dysplasia”, “three M syndrome”, “3-M syndrome”, “hypophosphatasia”, “fibrodysplasia ossificans progressive”, “type II collagen disorders”, “type II collagenopathies”, “type II collagenopathy”, “physical activity”, “exercise”, “sport”, “training”, and “physical fitness”, with the Boolean operators “AND” or “OR”. After reading the full texts of the studies, and according to previously defined eligibility criteria, fifteen studies met the inclusion criteria; however, there was not a single intervention study with physical exercise. Several cross-sectional, review, or qualitative studies presented a set of essential aspects that future intervention studies can consider when evaluating, prescribing, and implementing physical exercise programs, as they allowed the physical characterization of the SD population. This study demonstrated an apparent scarcity in the literature of experimental studies with physical exercise implementation in the SD population.

Infigratinib in children with achondroplasia: the PROPEL and PROPEL 2 studies

Background:

Achondroplasia is the most common short-limbed skeletal dysplasia resulting from gain-of-function pathogenic variants in fibroblast growth factor receptor 3 ( FGFR3) gene, a negative regulator of endochondral bone formation. Most treatment options are symptomatic, targeting medical complications. Infigratinib is an orally bioavailable, FGFR1–3 selective tyrosine kinase inhibitor being investigated as a direct therapeutic strategy to counteract FGFR3 overactivity in achondroplasia.

Objectives:

The main objective of PROPEL is to collect baseline data of children with achondroplasia being considered for future enrollment in interventional studies sponsored by QED Therapeutics. The objectives of PROPEL 2 are to obtain preliminary evidence of safety and efficacy of oral infigratinib in children with achondroplasia, to identify the infigratinib dose to be explored in future studies, and to characterize the pharmacokinetic (PK) profile of infigratinib and major metabolites.

Design:

PROPEL (NCT04035811) is a prospective, noninterventional clinical study designed to characterize the natural history and collect baseline data of children with achondroplasia over 6−24 months. PROPEL 2 (NCT04265651), a prospective, phase II, open-label study of infigratinib in children with achondroplasia, consists of a dose-escalation, dose-finding, and dose-expansion phase to confirm the selected dose, and a PK substudy.

Methods and analysis:

Children aged 3−11 years with achondroplasia who completed ⩾6 months in PROPEL are eligible for PROPEL 2. Primary endpoints include treatment-emergent adverse events and change from baseline in annualized height velocity. Four cohorts at ascending dose levels are planned for dose escalation. The selected dose will be confirmed in the dose-expansion phase.

Ethics:

PROPEL and PROPEL 2 are being conducted in accordance with the International Conference on Harmonization Good Clinical Practice guidelines, principles of the Declaration of Helsinki, and relevant human clinical research and data privacy regulations. Protocols have been approved by local health authorities, ethics committees, and institutions as applicable. Parents/legally authorized representatives are required to provide signed informed consent; signed informed assent by the child is also required, where applicable.

Discussion:

PROPEL and PROPEL 2 will provide preliminary evidence of the safety and efficacy of infigratinib as precision treatment of children with achondroplasia and will inform the design of future studies of FGFR-targeted agents in achondroplasia.

Registration:

ClinicalTrials.gov: NCT04035811; NCT04265651.

Lower Back Pain Heralding Cauda Equina Syndrome in a Patient With Achondroplasia

Achondroplasia is the most common cause of congenital dwarfism and is associated with multiple complications due to impaired skeletal development. Herein, we report a 21-year-old woman with achondroplasia experiencing lower back pain which progressed to lower limb weakness and urinary retention. Magnetic resonance imaging revealed decreased interpedicular distance and severe stenosis of the lumbosacral spinal canal. Cauda equina syndrome was diagnosed and she underwent laminectomy. After decompression, pain, muscle strength and bladder function improved significantly. This case highlights the importance of early recognition of spinal compression in patients with achondroplasia.

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.

Emerging therapies for Achondroplasia: changing the rules of the game

INTRODUCTION

Achondroplasia is the most common genetic cause of disproportionate short stature, affecting over 360,000 individuals. Serious complications contributing to significant morbidity in affected individuals include cranio-cervical junction compression and obstructive sleep apnoea. Current clinically available treatments are predominantly symptomatic, and associated with variable outcomes. We summarise the new precision investigational products that are currently in Phase 2 and Phase 3 clinical trials for the treatment of individuals with achondroplasia.

AREAS COVERED

Fibroblast growth factor receptor 3 (FGFR3), a membrane-spanning tyrosine kinase receptor, binds various fibroblast growth factors (FGF) to regulate the normal process of endochondral bone growth. Gain of FGFR3 function in individuals with achondroplasia results in inhibition of normal endochondral ossification. A greater understanding of these molecular pathways through animal models has led to the development of several targeted therapies being tested in children, which we discuss in this review.

EXPERT OPINION

The last decade has been game-changing in terms of new precision therapies for children with achondroplasia that have the potential to fundamentally change the natural history of this condition. The next decade will see how these therapies compare, if they might be used in combination, and evaluate the balance of their long-term benefits and harms.