The population-based prevalence of achondroplasia and thanatophoric dysplasia in selected regions of the US

Chapter 2: Non-invasive prenatal diagnosis

Non-invasive prenatal diagnosis of monogenic disorders is becoming integrated into routine clinical care for many indications. This is carried out by testing cell-free DNA extracted from the plasma portion of a maternal blood sample. The cell-free DNA is low in concentration, and consists of a mixture of maternal and fetally-derived DNA which are not easy to separate. Methods used therefore need to be rapid, sensitive and specific, including real-time PCR, digital PCR and next generation sequencing with complex algorithms. Testing may be required for pregnancies with an increased chance of a monogenic disorder due to family history or carrier status, or where there are specific abnormalities identified by ultrasound scan. In these situations, testing is considered to be diagnostic and therefore does not require confirmation by invasive testing. With increased access to genomic technologies, and more diagnoses for rare disease patients, future demand for NIPD and possibilities during pregnancy will continue.

Review of patients with achondroplasia: a single-center's experience with follow-up and associated morbidities

Achondroplasia (ACH; MIM #100,800), caused by a heterozygous gain of function pathogenic variant in the fibroblast growth factor receptor 3 gene (FGFR3; MIM*134,934), is the most prevalent and most readily identifiable cause of disproportionate short stature that is compatible with life. In addition, individuals with achondroplasia face significant medical, functional, and psychosocial challenges throughout their lives. This study assessed associated morbidities in patients with achondroplasia at a single center in Turkey. In this study, the clinical findings and associated morbidities of a group of patients with achondroplasia (n = 68) with clinical multidisciplinary follow-up at a single center between the years 2005-2023 are evaluated retrospectively. A total of 68 patients, 30 male (44.1%) and 38 female (55.9%), were evaluated. In the majority (84.2%) of patients, shortness of extremities was detected in the prenatal period at an average of 28.7 gestational weeks (± 3.6 SDS) with the aid of ultrasonography. More than half (n = 34/63, 54%) of the patients had a father of advanced paternal age (≥ 35 years). Among the complications, respiratory system manifestations, including obstructive sleep apnea (70%), ear-nose-throat manifestations including adenoid hypertrophy (56.6%) and otitis media (54.7%), neurological manifestations due to foramen magnum stenosis (53.2%), and skeletal manifestations including scoliosis (28.8%), are represented among the most common. The mortality rate was 7.3% (n = 5/68).Conclusion: This study not only represents the first retrospective analysis of the associated morbidities of patients with achondroplasia from a single center in Turkey but also will provide a reference point for future studies.

Fetal Skeletal Dysplasia

Skeletal dysplasias (SDs) are a diverse group of genetic disorders. Diagnosis can be difficult as many are rare and with varied presentations, but with knowledge of the most common SDs presenting prenatal and with an algorithm that uses both sonographic and MR imaging techniques, directed genetic testing and counseling can be provided for many families.

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.

Perioperative Complications Following Spine Surgery in Adult Patients with Achondroplasia

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To describe the common types of complications and their risk factors during spine surgery in patients with achondroplasia.

METHODS

A retrospective review was performed of medical records of adult achondroplasia patients who underwent spine surgery at our institution between 2007 and 2021. Inclusion criteria were achondroplasia and age >16 years. Surgical encounters were evaluated for durotomy, postoperative neurologic deficit, wound compromise, medical complications, and return to the operating room. Statistical analysis included evaluation of relationships across complications and fisher exact test applied to bivariate/categorical variables and t-test/ANOVA for continuous variables. Multivariable analysis using logistic regression was performed to account for patient characteristics.

RESULTS

Fifty-five patients with achondroplasia underwent 95 surgeries. Forty-nine percent of the surgeries involved a complication. These included durotomy (33.7%), neurologic deficit (11.6%), wound compromise (6.3%), and other medical complications (6.3%). Thirteen percent of surgeries required return to the operating room. The greatest number of complications occurred in thoracolumbar region (60.0%) compared to cervicothoracic (18.2%) and craniocervical junction (33.3%). Chronologically later surgical encounters had decreased complications and durotomies only occurred in thoracolumbar surgeries (45.7%).

CONCLUSIONS

Adult patients with achondroplasia undergoing surgery chronologically later in this set of consecutive patients were at a decreased risk for complications. Thoracolumbar surgeries were at the greatest risk for durotomies. Male sex was a risk factor for durotomy, while age was a risk factor for neurologic deficit. The potential for adverse surgical events should be considered when evaluating patients with achondroplasia for spine surgery. .

Natural disease course modeling of achondroplasia to evaluate the efficacy of recifercept in the absence of a placebo control arm in phase II study

While randomized, placebo-controlled, double-blinded clinical studies are the gold standard for evaluating the efficacy of investigational drugs, the use of placebo in children with achondroplasia should be limited because it provides no clinical benefit while exhausting study participants' treatment window. Recifercept is an investigational drug for treating children with achondroplasia aged 2-10 years. An alternative efficacy evaluation method, instead of a placebo control arm, was employed in the phase II study. Prior to participating in the phase II study, participants completed a natural history (NH) study. Based on the NH data, a multi-variate linear mixed effects natural disease course model of three anthropometric end points (standing height, sitting height, and arm span) was developed. The model was validated using published growth charts of children with achondroplasia. Subsequently, the model was used to simulate the natural growth trajectories (without any treatment) of the three anthropometric end points for the individuals enrolled in the phase II study. To quantify the efficacy of recifercept, the simulations were compared with the observations post-recifercept treatment in the phase II study. For all the tested doses of recifercept, at the individual level, the observations were comparable to the simulations at 6 and 12 months post-recifercept treatment, suggesting no treatment effect. The results contributed to the decision of terminating recifercept clinical development. This work delivers a framework that could eliminate the need for placebo in clinical trials yet provide sufficient evidence for evaluating the efficacy of an investigational drug.

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.

Review of published 467 achondroplasia patients: clinical and mutational spectrum

AIM

Achondroplasia is the most common of the skeletal dysplasias that cause fatal and disabling growth and developmental disorders in children, and is caused by a mutation in the fibroblast growth factor receptor, type 3 gene(FGFR3). This study aims to analyse the clinical characteristics and gene mutations of ACH to accurately determine whether a patient has ACH and to raise public awareness of the disease.

METHODS

The database of Pubmed, Cochrane Library, Wanfang and CNKI were searched with terms of "Achondroplasias" or "Skeleton-Skin-Brain Syndrome" or "Skeleton Skin Brain Syndrome" or "ACH" and "Receptor, Fibroblast Growth Factor, Type 3" or "FGFR3".

RESULTS

Finally, four hundred and sixty-seven patients with different FGFR3 mutations were enrolled. Of the 138 patients with available gender information, 55(55/138, 40%) were female and 83(83/138, 60%) were male. Among the patients with available family history, 47(47/385, 12%) had a family history and 338(338/385, 88%) patients were sporadic. The age of the patients ranged from newborn babies to 36 years old. The mean age of their fathers was 37 ± 7 years (range 31-53 years). Patients came from 12 countries and 2 continents, with the majority being Asian (383/432, 89%), followed by European (49/432, 11%). Short stature with shortened arms and legs was found in 112(112/112) patients, the abnormalities of macrocephaly in 94(94/112) patients, frontal bossing in 89(89/112) patients, genu valgum in 64(64/112) patients and trident hand were found in 51(51/112) patients. The most common mutation was p.Gly380Arg of the FGFR3 gene, which contained two different base changes, c.1138G > A and c.1138G > C. Ten rare pathogenic mutations were found, including c.831A > C, c.1031C > G, c.1043C > G, c.375G > T, c.1133A > G, c.1130T > G, c.833A > G, c.649A > T, c.1180A > T and c.970_971insTCTCCT.

CONCLUSION

ACH was caused by FGFR3 gene mutation, and c.1138G > A was the most common mutation type. This study demonstrates the feasibility of molecular genetic testing for the early detection of ACH in adolescents with short stature, trident hand, frontal bossing, macrocephaly and genu valgum.

Reverse Total Shoulder Arthroplasty in an Adult With Achondroplasia

Background: Achondroplasia can result in many skeletal manifestations, and degenerative osteoarthritis can develop in patients with achondroplasia. Morphologic changes to both the humerus and glenoid-short humeri with patulous metaphyses and a medialized glenoid-can cause challenges that must be overcome to achieve a successful surgical result in a patient with shoulder dysfunction. Because patients with achondroplasia have near-normal life expectancies, the operative shoulder must be functional as well as quite durable in the long term. In an achondroplastic dwarf with shoulder osteoarthritis and rotator cuff insufficiency, achieving functionality and durability requires the use of a reverse total shoulder arthroplasty (TSA). This procedure has its own set of issues, namely, baseplate fixation and correction of glenoid medialization, if present. Case Report: We present the case of an adult with achondroplastic dwarfism with shoulder osteoarthritis and rotator cuff insufficiency and report the 2-year clinical results for this patient after reverse TSA. Conclusion: Reverse TSA is a viable treatment option for adult achondroplastic patients with shoulder dysfunction. Careful preoperative planning is required to ensure a good clinical result in patients with potentially dysplastic anatomy.

Infigratinib, a selective FGFR1-3 tyrosine kinase inhibitor, alters dentoalveolar development at high doses

BACKGROUND

Fibroblast growth factor receptor-3 (FGFR3) gain-of-function mutations are linked to achondroplasia. Infigratinib, a FGFR1-3 tyrosine kinase inhibitor, improves skeletal growth in an achondroplasia mouse model. FGFs and their receptors have critical roles in developing teeth, yet effects of infigratinib on tooth development have not been assessed. Dentoalveolar and craniofacial phenotype of Wistar rats dosed with low (0.1 mg/kg) and high (1.0 mg/kg) dose infigratinib were evaluated using micro-computed tomography, histology, and immunohistochemistry.

RESULTS

Mandibular third molars were reduced in size and exhibited aberrant crown and root morphology in 100% of female rats and 80% of male rats at high doses. FGFR3 and FGF18 immunolocalization and extracellular matrix protein expression were unaffected, but cathepsin K (CTSK) was altered by infigratinib. Cranial vault bones exhibited alterations in dimension, volume, and density that were more pronounced in females. In both sexes, interfrontal sutures were significantly more patent with high dose vs vehicle.

CONCLUSIONS

High dose infigratinib administered to rats during early stages affects dental and craniofacial development. Changes in CTSK from infigratinib in female rats suggest FGFR roles in bone homeostasis. While dental and craniofacial disruptions are not expected at therapeutic doses, our findings confirm the importance of dental monitoring in clinical studies.

Achondroplasia natural history study (CLARITY): 60-year experience in orthopedic surgery from four skeletal dysplasia centers

BACKGROUND

The purpose of this study was to describe the frequency and risk factors for orthopedic surgery in patients with achondroplasia. CLARITY (The Achondroplasia Natural History Study) includes clinical data from achondroplasia patients receiving treatment at four skeletal dysplasia centers in the United States from 1957 to 2018. Data were entered and stored in a Research Electronic Data Capture (REDCap) database.

RESULTS

Information from one thousand three hundred and seventy-four patients with achondroplasia were included in this study. Four hundred and eight (29.7%) patients had at least one orthopedic surgery during their lifetime and 299 (21.8%) patients underwent multiple procedures. 12.7% (n = 175) of patients underwent spine surgery at a mean age at first surgery of 22.4 ± 15.3 years old. The median age was 16.7 years old (0.1-67.4). 21.2% (n = 291) of patients underwent lower extremity surgery at a mean age at first surgery of 9.9 ± 8.3 years old with a median age of 8.2 years (0.2-57.8). The most common spinal procedure was decompression (152 patients underwent 271 laminectomy procedures), while the most common lower extremity procedure was osteotomy (200 patients underwent 434 procedures). Fifty-eight (4.2%) patients had both a spine and lower extremity surgery. Specific risk factors increasing the likelihood of orthopedic surgery included: patients with hydrocephalus requiring shunt placement having higher odds of undergoing spine surgery (OR 1.97, 95% CI 1.14-3.26); patients having a cervicomedullary decompression also had higher odds of undergoing spine surgery (OR 1.85, 95% CI 1.30-2.63); and having lower extremity surgery increased the odds of spine surgery (OR 2.05, 95% CI 1.45-2.90).

CONCLUSIONS

Orthopedic surgery was a common occurrence in achondroplasia with 29.7% of patients undergoing at least one orthopedic procedure. Spine surgery (12.7%) was less common and occurred at a later age than lower extremity surgery (21.2%). Cervicomedullary decompression and hydrocephalus with shunt placement were associated with an increased risk for spine surgery. The results from CLARITY, the largest natural history study of achondroplasia, should aid clinicians in counseling patients and families about orthopedic surgery.

Current and emerging therapies for Achondroplasia: The dawn of precision medicine

Achondroplasia is a rare disease affecting bone growth and is caused by a missense mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. In the past few years, there were multiple experimental drugs entering into clinical trials for treating achondroplasia including vosoritide, the first precision medicine approved for this indication. This perspective presents the mechanism of action, benefit, and potential mechanistic limitation of the drugs currently being evaluated in clinical trials for achondroplasia. This article also discusses the potential impact of those drugs not only in increasing the growth of individuals living with achondroplasia but also in improving their quality of life.

What to Expect of Feeding Abilities and Nutritional Aspects in Achondroplasia Patients: A Narrative Review

Achondroplasia is an autosomal dominant genetic disease representing the most common form of human skeletal dysplasia: almost all individuals with achondroplasia have identifiable mutations in the fibroblast growth factor receptor type 3 (FGFR3) gene. The cardinal features of this condition and its inheritance have been well-established, but the occurrence of feeding and nutritional complications has received little prominence. In infancy, the presence of floppiness and neurological injury due to foramen magnum stenosis may impair the feeding function of a newborn with achondroplasia. Along with growth, the optimal development of feeding skills may be affected by variable interactions between midface hypoplasia, sleep apnea disturbance, and structural anomalies. Anterior open bite, prognathic mandible, retrognathic maxilla, and relative macroglossia may adversely impact masticatory and respiratory functions. Independence during mealtimes in achondroplasia is usually achieved later than peers. Early supervision of nutritional intake should proceed into adolescence and adulthood because of the increased risk of obesity and respiratory problems and their resulting sequelae. Due to the multisystem involvement, oral motor dysfunction, nutrition, and gastrointestinal issues require special attention and personalized management to facilitate optimal outcomes, especially because of the novel therapeutic options in achondroplasia, which could alter the progression of this rare disease.

Whole exome sequencing combined with dynamic ultrasound assessments for fetal skeletal dysplasias: 4 case reports

RATIONALE

Fetal skeletal anomalies are one of the most common and potentially pathogenic developmental abnormalities detected by ultrasound screening. Any suspected fetal skeletal dysplasias often require further comprehensive evaluations.

PATIENT CONCERNS

Here 4 families with adverse fetal skeletal system histories were enrolled, including their histories of gestation, childbirth, familial skeletal abnormalities, and pregnancy outcomes. The corresponding diagnosis were done by whole exome sequencing (WES) combined with dynamic examination.

DIAGNOSIS

All of the families were definitively diagnosed through cytogenetics, molecular genetics, ultrasound, combined with multidisciplinary evaluation. Both of the fetuses in case 1 and case 2 were diagnosed with thanatophoric dysplasia type I, while the neonate in case 3 was diagnosed with Apert syndrome and a 3-years-old proband daughter with Crouzon syndrome in case 4.

INTERVENTIONS

We conducted karyotyping, copy number variation sequencing (CNV-seq), combined with WES to evaluate genetic conditions of abnormal fetus, neonate or proband patient. WES was preferred to obtain a relatively definitive diagnosis.

OUTCOMES

In cases 1 and 2, the families decided to choose termination of pregnancy due to fatal dysplasias. The couple in case 3, delivered a female baby diagnosed with Apert syndrome. Fortunately, in case 4, the family, which had a 3-years-old baby with Crouzon syndrome, gave birth to a healthy baby through prenatal diagnosis.

LESSONS SUBSECTIONS

Invasive prenatal diagnosis and dynamic assessments for the management of fetal skeletal dysplasias could contribute to revealing possible causes of fetal skeletal abnormalities and help clinicians conduct further genetic counseling in clinical practice.

Posterior Vertebral Column Resection (pVCR) for Severe Thoracolumbar Kyphosis in Patients With Achondroplasia

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

We aimed to evaluate the safety and validity of posterior vertebral column resection (pVCR) for severe thoracolumbar kyphosis (TLK) in the achondroplasia (ACH) patients.

METHODS

Seven ACH patients (male: female = 6:1) who underwent pVCR procedures due to severe TLK from December 2008 to December 2017 in the authors' hospital were included in this retrospective study. Their mean follow-up duration was 67 ± 35 months. Their clinical characteristics, radiologic characteristics, surgical characteristics and surgical complications were reviewed.

RESULTS

A total of 8 vertebrae were removed with an average of 5 ± 2 levels of decompression and 9 ± 2 segments instrumented. The mean correction rates of TLKs and the main curves were 73 ± 15% and 87 ± 6%, respectively. Five patients (71%) had preoperative neurological symptoms with a mean Japanese Orthopedic Association (JOA) score of 8 ± 3 points. Their neurological functions were all improved, with a recovery rate of 78 ± 32% for the JOA score at the last follow-up. Four patients (57%) suffered from surgical complications, including rod breakages (43%), neurological complications (28%), dural tears (14%), cerebrospinal fluid leaks (14%) and proximal junction kyphosis (14%).

CONCLUSIONS

pVCR can offer a good correction for TLK and improve neurological function with extensive laminectomies in ACH patients. But the morbidity of surgical complications is relatively high. Therefore, it is a reserved surgical option for severe TLK in ACH patients by experienced spinal surgeons, especially with apical markedly hypoplastic vertebrae.

Thanatophoric Dysplasia: A Report of 2 Cases with Antenatal Misdiagnosis

Thanatophoric dysplasia (TD) is a rare but uniformly lethal inherited disorder of the skeletal system resulting from defects in the fibroblast growth factor receptor-3 gene on the short arm of chromosome ##4. It is characterised by pronounced shortening of the tubular bones resulting in significant short stature, macrocephaly, a funnel-shaped chest, protuberant abdomen, redundant skin in the limbs, and typical facies among others. The two clinical types of TD are differentiated by typical cranial and tubular bone configurations. Antenatal diagnosis is usually made in the last trimester and corroborated at birth. We present 2 cases of TD seen at Barau Dikko Teaching Hospital (BDTH) between January and August 2021 to highlight the potential difficulty with antenatal diagnosis, its diagnostic features, and associated early postnatal fatality. The antenatal diagnosis was missed in both cases in spite of repeated 2^nd and 3^rd-trimester sonographic examinations. Both babies presented with remarkable micromelic short stature with the telephone-handle appearance of the femoral bones characteristic of type 1 TD, developed progressive respiratory distress at birth, and died within 36 hours of life despite respiratory support with Bubble CPAP. These cases are discussed along with a review of existing relevant literature.

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.

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.

Achondroplasia in Latin America: practical recommendations for the multidisciplinary care of pediatric patients

Background

Achondroplasia is the most common bone dysplasia associated with disproportionate short stature, and other comorbidities, such as foramen magnum stenosis, thoracolumbar kyphosis, lumbar hyperlordosis, genu varum and spinal compression. Additionally, patients affected with this condition have higher frequency of sleep disorders, ear infections, hearing loss and slowed development milestones. Considering these clinical features, we aimed to summarize the regional experts’ recommendations for the multidisciplinary management of patients with achondroplasia in Latin America, a vast geographic territory with multicultural characteristics and with socio-economical differences of developing countries.

Methods

Latin American experts (from Argentina, Brazil, Chile and Colombia) particiáted of an Advisory Board meeting (October 2019), and had a structured discussion how patients with achondroplasia are followed in their healthcare centers and punctuated gaps and opportunities for regional improvement in the management of achondroplasia.

Results

Practical recommendations have been established for genetic counselling, prenatal diagnosis and planning of delivery in patients with achondroplasia. An outline of strategies was added as follow-up guidelines to specialists according to patient developmental phases, amongst them neurologic, orthopedic, otorhinolaryngologic, nutritional and anthropometric aspects, and related to development milestones. Additionally, the role of physical therapy, physical activity, phonoaudiology and other care related to the quality of life of patients and their families were discussed. Preoperative recommendations to patients with achondroplasia were also included.

Conclusions

This study summarized the main expert recommendations for the health care professionals management of achondroplasia in Latin America, reinforcing that achondroplasia-associated comorbidities are not limited to orthopedic concerns.

A registry of achondroplasia: a 6-year experience from the Czechia and Slovak Republic

Background

Achondroplasia (ACH) is one of the most prevalent genetic forms of short-limbed skeletal dysplasia, caused by gain-of-function mutations in the receptor tyrosine kinase FGFR3. In August 2021, the C-type natriuretic peptide (CNP) analog vosoritide was approved for the treatment of ACH. A total of six other inhibitors of FGFR3 signaling are currently undergoing clinical evaluation for ACH. This progress creates an opportunity for children with ACH, who may gain early access to the treatment by entering clinical trials before the closure of their epiphyseal growth plates and cessation of growth. Pathophysiology associated with the ACH, however, demands a long observational period before admission to the interventional trial. Public patient registries can facilitate the process by identification of patients suitable for treatment and collecting the data necessary for the trial entry.

Results

In 2015, we established the prospective ACH registry in the Czechia and the Slovak Republic (http://www.achondroplasia-registry.cz). Patient data is collected through pediatric practitioners and other relevant specialists. After informed consent is given, the data is entered to the online TrialDB system and stored in the Oracle 9i database. The initial cohort included 51 ACH children (average age 8.5 years, range 3 months to 14 years). The frequency of selected neurological, orthopedic, or ORL diagnoses is also recorded. In 2015–2021, a total of 89 measurements of heights, weights, and other parameters were collected. The individual average growth rate was calculated and showed values without exception in the lower decile for the appropriate age. Evidence of paternal age effect was found, with 58.7% of ACH fathers older than the general average paternal age and 43.5% of fathers older by two or more years. One ACH patient had orthopedic limb extension and one patient received growth hormone therapy. Low blood pressure or renal impairment were not found in any patient.

Conclusion

The registry collected the clinical information of 51 pediatric ACH patients during its 6 years of existence, corresponding to ~ 60% of ACH patients living in the Czechia and Slovak Republic. The registry continues to collect ACH patient data with annual frequency to monitor the growth and other parameters in preparation for future therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02374-x.

Clinical management and emerging therapies of FGFR3-related skeletal dysplasia in childhood

Skeletal dysplasia is a diverse group of disorders that affect bone development and morphology. Currently, approximately 461 different genetic skeletal disorders have been identified, with over 430 causative genes. Among these, fibroblast growth factor receptor 3 (FGFR3)-related skeletal dysplasia is a relatively common subgroup of skeletal dysplasia. Pediatric endocrinologists may encounter a suspected case of skeletal dysplasia in their practice, especially when evaluating children with short stature. Early and accurate diagnosis of FGFR3-related skeletal dysplasia is essential for timely management of complications and genetic counseling. This review summarizes 5 representative and distinct entities of skeletal dysplasia caused by pathogenic variants in FGFR3 and discusses emerging therapies for FGFR3-related skeletal dysplasias.

Prenatal trio-based whole exome sequencing in fetuses with abnormalities of the skeletal system

Whole exome sequencing (WES) could yield diagnostic significance in the prenatal diagnosis of skeletal abnormalities. But the phenotypes of fetuses with skeletal abnormalities are heterogenous, and the clinical information we could obtain from an ongoing pregnancy is limited, making the prenatal diagnosis complicated. Therefore, the following interpretation and genetic counseling remain a challenge for clinicians. The aim of this study is to present and investigate the utility of trio-based WES in five fetuses with skeletal anomalies. Five trios with fetal ultrasonic skeletal anomalies were recruited in our study. Fetal specimens and parental peripheral blood were subjected to WES. The fetal skeletal abnormalities were presented through ultrasound scanning images. Fetal WES results showed variants in the PPIB, CHST3, COL1A1, and FGFR3 genes in the five trios. Inherited variants were found in two of the trios, while de novo variants were observed in three of them. Two novel compound heterozygous variants (c.437C > A and c.1044C > G) in CHST3 were identified. We presented five trios with fetal skeletal anomalies, found two novel variants and broadened the spectrum of variants associated with skeletal abnormalities, which would help the establishment of genotype-phenotype relationship in the prenatal setting. Trio-based WES could assist the prenatal diagnosis and genetic counseling of fetuses with skeletal abnormalities.

Long-Term Results of Posterior Vertebral Column Resection for Severe Thoracolumbar Kyphosis with Achondroplastic Patients: A Case Series

Background and Objectives: Thoracolumbar kyphosis is one of the most frequent skeletal manifestations in patients with achondroplasia. Few papers have been published on the surgical treatment of this condition, especially in skeletally mature patients. With this study, we presented a retrospective case series of long-term surgical results for achondroplastic patients with severe thoracolumbar kyphosis. This study was conducted to evaluate the outcome of surgical treatment for thoracolumbar kyphosis in patients associated with achondroplasia presenting with paraparesis. Materials and Methods: Three patients with achondroplasia who developed neurologic deficits due to severe thoracolumbar kyphosis and underwent surgical treatment were evaluated (mean age 22.3 years; mean follow-up 9.3 years). All patients were treated with posterior vertebral column resection (p-VCR) of hypoplastic apical vertebrae with a cage and segmental instrumentation. Neurologic outcomes (JOA scores), correction of kyphosis, and operative complications were assessed. Results: All patients had back pain, neurological deficits, and urinary disturbance before surgery. The average preoperative JOA score was 8.3/11 points, which was improved to 10.7/11 points at the final follow-up (mean recovery rate 83%). All patients obtained neurologic improvement after surgery. The mean preoperative kyphotic angle was 117° (range 103°–126°). The postoperative angles averaged 37° (range 14°–57°), resulting in a mean correction rate of 67%. All patients had postoperative complications such as rod breakage and/or surgical site infection. Conclusions: The long-term results of p-VCR were acceptable for treating thoracolumbar kyphosis in patients with achondroplasia. To perform this p-VCR safely, spinal navigation and neuromonitoring are inevitable when resecting non anatomical fused vertebrae and ensuring correct pedicle screw insertion. However, surgical complications such as rod breakage and surgical site infection may occur at a high rate, making informed consent very important when surgery is indicated.

Disease-Specific Health Disparities: A Targeted Review Focusing on Race and Ethnicity

Background: Wide disparities in health status exist in the United States across race and ethnicity, broadly driven by social determinants of health—most notably race and ethnic group differences in income, education, and occupational status. However, disparities in disease frequency or severity remain underappreciated for many individual diseases whose distribution in the population varies. Such information is not readily accessible, nor emphasized in treatment guidelines or reviews used by practitioners. Specifically, a summary on disease-specific evidence of disparities from population-based studies is lacking. Our goal was to summarize the published evidence for specific disease disparities in the United States so that this knowledge becomes more widely available “at the bedside”. We hope this summary stimulates health equity research at the disease level so that these disparities can be addressed effectively. Methods: A targeted literature review of disorders in Pfizer’s current pipeline was conducted. The 38 diseases included metabolic disorders, cancers, inflammatory conditions, dermatologic disorders, rare diseases, and infectious targets of vaccines under development. Online searches in Ovid and Google were performed to identify sources focused on differences in disease rates and severity between non-Hispanic Whites and Black/African Americans, and between non-Hispanic Whites and Hispanics. As a model for how this might be accomplished for all disorders, disparities in disease rates and disease severity were scored to make the results of our review most readily accessible. After primary review of each condition by one author, another undertook an independent review. Differences between reviewers were resolved through discussion. Results: For Black/African Americans, 29 of the 38 disorders revealed a robust excess in incidence, prevalence, or severity. After sickle cell anemia, the largest excesses in frequency were identified for multiple myeloma and hidradenitis suppurativa. For Hispanics, there was evidence of disparity in 19 diseases. Most notable were metabolic disorders, including non-alcoholic steatohepatitis (NASH). Conclusions: This review summarized recent disease-specific evidence of disparities based on race and ethnicity across multiple diseases, to inform clinicians and health equity research. Our findings may be well known to researchers and specialists in their respective fields but may not be common knowledge to health care providers or public health and policy institutions. Our hope is that this effort spurs research into the causes of the many disease disparities that exist in the United States.

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.

Disease-specific complications and multidisciplinary interventions in achondroplasia

Achondroplasia (ACH) is the most common skeletal dysplasia and characterized by a disproportionate short stature, macrocephaly with frontal bossing, exaggerated lumbar lordosis, and trident hands. It is induced by activated mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. In addition to short stature, patients with ACH have a high prevalence of medical complications, including upper airway obstructive apnea, increased mortality, foramen magnum stenosis, hydrocephalus, developmental delay, recurrent ear infections, genu varum, obesity, and spinal canal stenosis, throughout their whole life. Several investigational drugs that modulate abnormal FGFR3 signaling have recently emerged, vosoritide being the most developed. This review presents the different disease-specific complications of ACH occurring in neonates, infants, childhood, adolescent, and adults and reports the current multidisciplinary interventions for these various complications. Moreover, we propose treatment strategies for children with ACH from the perspective of quality of life in adulthood.

Emerging therapies for the treatment of rare pediatric bone disorders

In recent years, new therapies for the treatment of rare pediatric bone disorders have emerged, guided by an increasing understanding of the genetic and molecular etiology of these diseases. Herein, we review three such disorders, impacted by debilitating deficits in bone mineralization or cartilage ossification, as well as the novel disease-modifying drugs that are now available to treat these conditions. Specifically, we discuss asfotase alfa, burosumab-twza, and vosoritide, for the treatment of hypophosphatasia, X-linked hypophosphatemia and achondroplasia, respectively. For each skeletal disorder, an overview of the clinical phenotype and natural history of disease is provided, along with a discussion of the clinical pharmacology, mechanism of action and FDA indication for the relevant medication. In each case, a brief review of clinical trial data supporting drug development for each medication is provided. Additionally, guidance as to drug dosing and long-term monitoring of adverse events and pediatric efficacy is presented, to aid the clinician seeking to utilize these novel therapies in their practice, or to become familiar with the healthcare expectations for children receiving these medications through specialized multidisciplinary clinics. The availability of these targeted therapies now significantly augments treatment options for conditions in which past therapy has relied upon less specific, symptomatic medical and orthopedic care.

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.

Neurosurgical Evaluation and Management of Adults with Achondroplasia

Much of the current medical discussion for within centers for skeletal dysplasia and specifically patients with achondroplasia focuses on infancy and early childhood. Most neurosurgical concerns arise due to a defect in the endochondral ossification, resulting on early fusion of the synchondrosis. As patients age, the neurosurgical focus shifts from primarily cranial to spinal concerns. Often pediatric neurosurgeons may continue to follow their patients with skeletal dysplasia. However, general adult neurosurgeons and orthopedic surgeons may see these graduated adults in their practice. This article provides a review of the common neurosurgical concerns for patients with achondroplasia.

Neurosurgical Evaluation and Management of Children with Achondroplasia

Achondroplasia is the most common of skeletal dysplasias and is caused by a defect in endochondral bone formation. In addition to skeletal deformities, patients with achondroplasia possess significant abnormalities of the axial skeleton, including small skull base with a narrowed foramen magnum and small vertebral bodies with shortened pedicles. Consequently, patients with achondroplasia are at risk of several severe neurologic conditions, such as cervicomedullary compression, spinal stenosis, and hydrocephalus, which frequently require the attention of a neurosurgeon. This article provides an updated review on the neurosurgical evaluation and care of children with Achondroplasia.

Development and validation of an expanded targeted sequencing panel for non-invasive prenatal diagnosis of sporadic skeletal dysplasia

Background

Skeletal dysplasia (SD) is one of the most common inherited neonatal disorders worldwide, where the recurrent pathogenic mutations in the FGFR2, FGFR3, COL1A1, COL1A2 and COL2A1 genes are frequently reported in both non-lethal and lethal SD. The traditional prenatal diagnosis of SD using ultrasonography suffers from lower accuracy and performed at latter gestational stage. Therefore, it remains in desperate need of precise and accurate prenatal diagnosis of SD in early pregnancy. With the advancements of next-generation sequencing (NGS) technology and bioinformatics analysis, it is feasible to develop a NGS-based assay to detect genetic defects in association with SD in the early pregnancy.

Methods

An ampliseq-based targeted sequencing panel was designed to cover 87 recurrent hotspots reported in 11 common dominant SD and run on both Ion Proton and NextSeq550 instruments. Thirty-six cell-free and 23 genomic DNAs were used for assay developed. Spike-in DNA prepared from standard sample harboring known mutation and normal sample were also employed to validate the established SD workflow. Overall performances of coverage, uniformity, and on-target rate, and the detecting limitations on percentage of fetal fraction and read depth were evaluated.

Results

The established targeted-seq workflow enables a single-tube multiplex PCR for library construction and shows high amplification efficiency and robust reproducibility on both Ion Proton and NextSeq550 platforms. The workflow reaches 100% coverage and both uniformity and on-target rate are > 96%, indicating a high quality assay. Using spike-in DNA with different percentage of known FGFR3 mutation (c.1138 G > A), the targeted-seq workflow demonstrated the ability to detect low-frequency variant of 2.5% accurately. Finally, we obtained 100% sensitivity and 100% specificity in detecting target mutations using established SD panel.

Conclusions

An expanded panel for rapid and cost-effective genetic detection of SD has been developed. The established targeted-seq workflow shows high accuracy to detect both germline and low-frequency variants. In addition, the workflow is flexible to be conducted in the majority of the NGS instruments and ready for routine clinical application. Taken together, we believe the established panel provides a promising diagnostic or therapeutic strategy for prenatal genetic testing of SD in routine clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01063-1.

Otolaryngology Utilization in Patients With Achondroplasia: Results From the CLARITY Study

OBJECTIVES/HYPOTHESIS

To quantify otolaryngologic surgery utilization in patients with achondroplasia, and to identify any changes in utilization over the past four decades.

STUDY DESIGN

Retrospective cohort study.

METHODS

A retrospective cohort study of 1,374 patients with achondroplasia enrolled in the CLARITY retrospective cohort study at four centers of multi-specialty care for patients with achondroplasia. Otolaryngologic surgeries are presented by birth cohort decade. The main outcomes were number of primary and additional otolaryngologic procedures; age at surgery; likelihood of repeated surgery; temporal trends in surgical utilization.

RESULTS

In this cohort of 1,374 patients with achondroplasia, 620 (45.1%) had pharyngeal surgery at least once, 150 (10.9%) had pharyngeal surgery on more than one occasion, and patients who had adenoidectomy first were 2.68 times more likely to require a second pharyngeal surgery than those who had adenotonsillectomy. Seven hundred and seventy-nine (56.7%) had tympanostomy tubes placed at least once, and 447 (32.5%) had tympanostomy tubes placed more than one time. Age at first pharyngeal surgery decreased by 1.2 years per birth cohort decade, and age at tympanostomy tube placement decreased by 1.1 years per decade.

CONCLUSIONS

Patients with achondroplasia often require otolaryngologic surgery, particularly adenoidectomy and/or tonsillectomy as well as tympanostomy tube placement. Such surgery is performed now more frequently and at younger ages than in earlier decades. While otolaryngologic disease associated with achondroplasia is now recognized earlier and treated more frequently, long-term outcome studies are needed.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

An intronic variant disrupts mRNA splicing and causes FGFR3-related skeletal dysplasia

OBJECTIVES

Achondroplasia and hypochondroplasia are the most common forms of disproportionate short stature, of which the vast majority of cases can be attributed to the hotspot missense mutations in the gene FGFR3. Here we presented cases with a novel cryptic splicing variant of FGFR3 gene and aimed to interrogate the variant pathogenicity.

CASE PRESENTAITON

In whole exome sequencing of two patients with hypochondroplasia-like features, a de novo intronic variant c.1075 + 95C>G was identified, predicted to alter mRNA splicing. Minigene assay showed that this intronic variant caused retention of a 90-nucleotide segment of intron 8 in mRNA, resulting in a 30-amino acid insertion at the extracellular domain of the protein. This is the first likely pathogenic splicing variant identified in the FGFR3 gene and was detected in one additional patient among 26 genetically unresolved patients.

CONCLUSTIONS

Our results strongly suggest that c.1075 + 95C>G is a recurrent mutation and should be included in genetic testing of FGFR3 especially for those patients with equivocal clinical findings and no exonic mutations identified.

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.

Achondroplasia Natural History Study (CLARITY): a multicenter retrospective cohort study of achondroplasia in the United States

PURPOSE

Achondroplasia is the most common short stature skeletal dysplasia (1:20,000-30,000), but the risk of adverse health outcomes from cardiovascular diseases, pain, poor function, excess weight, and sleep apnea is unclear. A multicenter retrospective natural history study was conducted to understand medical and surgical practices in achondroplasia.

METHODS

Data from patients with achondroplasia evaluated by clinical geneticists at Johns Hopkins University, A.I. duPont Hospital for Children, McGovern Medical School UTHealth, and University of Wisconsin were populated into a REDCap database. All available retrospective medical records of anthropometry (length/height, weight, occipitofrontal circumference), surgery, polysomnography (PSG), and imaging (e.g., X-ray, magnetic resonance imaging) were included.

RESULTS

Data from 1,374 patients (48.8% female; mean age 15.4 ± 13.9 years) constitute the primary achondroplasia cohort (PAC) with 496 subjects remaining clinically active and eligible for prospective studies. Within the PAC, 76.0% had a de novo FGFR3 pathologic variant and 1,094 (79.6%) had one or more achondroplasia-related surgeries. There are ≥37,000 anthropometry values, 1,631 PSGs and 10,727 imaging studies.

CONCLUSION

This is the largest multicenter achondroplasia natural history study, providing a vast array of medical information for use in caring for these patients. This well-phenotyped cohort is a reference population against which future medical and surgical interventions can be compared.

An RNA aptamer restores defective bone growth in FGFR3-related skeletal dysplasia in mice

Achondroplasia is the most prevalent genetic form of dwarfism in humans and is caused by activating mutations in FGFR3 tyrosine kinase. The clinical need for a safe and effective inhibitor of FGFR3 is unmet, leaving achondroplasia currently incurable. Here, we evaluated RBM-007, an RNA aptamer previously developed to neutralize the FGFR3 ligand FGF2, for its activity against FGFR3. In cultured rat chondrocytes or mouse embryonal tibia organ culture, RBM-007 rescued the proliferation arrest, degradation of cartilaginous extracellular matrix, premature senescence, and impaired hypertrophic differentiation induced by FGFR3 signaling. In cartilage xenografts derived from induced pluripotent stem cells from individuals with achondroplasia, RBM-007 rescued impaired chondrocyte differentiation and maturation. When delivered by subcutaneous injection, RBM-007 restored defective skeletal growth in a mouse model of achondroplasia. We thus demonstrate a ligand-trap concept of targeting the cartilage FGFR3 and delineate a potential therapeutic approach for achondroplasia and other FGFR3-related skeletal dysplasias.

Revisiting Skeletal Dysplasias in the Newborn

With over 400 reported disorders, the skeletal dysplasias represent a myriad of molecularly-based skeletal abnormalities. Arising from errors in skeletal development, the clinical spectrum of disease evolves through an affected individual's life. The naming and grouping of these disorders are ever-changing, but the fundamentals of diagnosis remain the same and are accomplished through a combination of prenatal ultrasonography and postnatal physical examination, radiography, and genetic analysis. Although some disorders are lethal in the perinatal and neonatal periods, other disorders allow survival into infancy, childhood, and even adulthood with relatively normal lives. The foundation of management for an affected individual is multidisciplinary care. Medical advances have offered new insights into reducing common morbidities through pharmacologic means. This review summarizes the normal skeletal development and discusses the 3 most common skeletal dysplasias that can affect the newborn.

A novel de novo mutation in COL2A1 gene associated with fetal skeletal dysplasia

OBJECTIVE

Skeletal dysplasias, caused by genetic mutations, are a heterogenous group of heritable disorders affecting bone development during fetal life. Stickler syndrome, one of the skeletal dysplasias, is an autosomal dominant connective tissue disorder caused by abnormal collagen synthesis owing to a genetic mutation in COL2A1.

CASE REPORT

We present the case of a 38-year-old multipara woman whose first trimester screening showed a normal karyotype. However, the bilateral femur and humerus length symmetrically shortened after 20 weeks. Next-generation sequencing for mutations in potential genes leading to skeletal dysplasia detected a novel de novo mutation (c.1438G > A, p.Gly480Arg) in COL2A1, causing Stickler syndrome type 1. This pathogenic mutation might impair or destabilize the collagen structure, leading to collagen type II, IX, and XI dysfunction.

CONCLUSION

We identified a novel de novo mutation in COL2A1 related to the STL1 syndrome and delineated the extent of the skeletal dysplasia disease spectrum.

Effect of paternal age on offspring birth defects: a systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis was aimed at determining whether paternal age is a risk factor for offspring birth defects.

RESULTS

A total of 38 and 11 studies were included in the systematic review and meta-analysis, respectively. Compared with reference, fathers aged 25 to 29, young fathers (< 20 years) could increase the risk of urogenital abnormalities (OR: 1.50, 95 % CI: 1.03-2.19) and chromosome disorders (OR: 1.38, 95 % CI: 1.12-1.52) in their offsprings; old fathers (≥ 40 years) could increase the risk of cardiovascular abnormalities (OR: 1.10, 95 % CI: 1.01-1.20), facial deformities (OR: 1.08, 95 % CI: 1.00-1.17), urogenital abnormalities (OR: 1.28, 95 % CI: 1.07-1.52), and chromosome disorders (OR: 1.30, 95 % CI: 1.12-1.52).

CONCLUSIONS

Our study indicated that paternal age is associated with a moderate increase in the incidence of urogenital and cardiovascular abnormalities, facial deformities, and chromosome disorders.

METHODS

PubMed, Web of Science, the Cochrane Library, and Embase were searched for relevant literatures from 1960 to February 2020. The systematic review follows PRISMA guidelines. Relevant meta-analyses were performed.

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.

Chondrodysplasias and Aneurysmal Thoracic Aortopathy: An Emerging Tale of Molecular Intersection

Although at first glance chondrodysplasia and aneurysmal thoracic aortopathy seem oddly dissimilar, recent lines of evidences indicate that they share molecular similarities. Chondrodysplasias are a group of skeletal disorders characterized by genetic defects in hyaline cartilage. Aneurysmal thoracic aortopathy is the pathological enlargement of the thoracic aorta due to wall weakness, along with its ensuing life-threatening complications (i.e., aortic dissection and/or rupture). Extracellular matrix dysregulation, abnormal TGF-β signaling, and, to a more limited extent, endoplasmic reticulum stress emerge as common disease processes. In this review we provide a comprehensive overview of the genetic and pathomechanistic overlap as well as of how these commonalities can guide treatment strategies for both disease entities.

The role of sonographic phenotyping in delivering an efficient noninvasive prenatal diagnosis service for FGFR3-related skeletal dysplasias

OBJECTIVES

To evaluate the diagnostic yield of noninvasive prenatal diagnosis (NIPD) for FGFR3-related skeletal dysplasias and assess the accuracy of referrals based on sonographic findings to inform guidelines for referral.

METHODS

We retrospectively reviewed laboratory and referral records from 2012 to 2018 to ascertain all NIPD tests performed using our next generation sequencing panel to detect FGFR3 mutations. We calculated the diagnostic yield of the test overall and when sub-divided according to the phenotypic features identified on ultrasound before testing. Pregnancy outcomes were ascertained wherever possible from referring centers.

RESULTS

Of 335 tests, 261 were referred because of sonographic findings, of which 80 (31.3%) had a mutation. The diagnostic yield when short limbs were the only abnormal sonographic feature reported was 17.9% (30/168), increasing to 48.9% (23/47) in the presence of one, and 82.6% (19/23) in the presence of two or more characteristic features in addition to short limbs.

CONCLUSIONS

Accurate sonographic phenotyping can maximise the diagnostic yield of NIPD in fetuses suspected to have FGFR3-related skeletal dysplasias. We suggest that clear guidelines for referral are necessary to increase benefits, decrease costs by preventing unnecessary NIPD, and potentially allow first-line broader spectrum testing for fetuses where the aetiology may be more heterogeneous.

Cardiac interventions in patients with achondroplasia: a systematic review

Patients with achondroplasia and other causes of dwarfism suffer from increased rates of cardiovascular disease relative to the remainder of the population. Few studies have examined these patients when undergoing cardiac surgery or percutaneous intervention. This systematic review examines the literature to determine outcomes following cardiac intervention in this unique population. An electronic search was performed in the English literature to identify all reports of achondroplasia, dwarfism, and cardiac intervention. Of the 5,274 articles identified, 14 articles with 14 cases met inclusion criteria. Patient-level data was extracted and analyzed. Median patient age was 55.5 [interquartile ranges (IQR), 43.8, 59.8] years, median height 102.0 [98.8, 112.5] cm, median BMI 32.1 [27.0, 45.9], and 57.1% (8/14) were male. Of these 14 patients, nine had the following documented skeletal abnormalities: 66.7% (6/9) had scoliosis, 66.7% (6/9) had kyphosis, 11.1% (1/9) had lordosis, 11.1% (1/9) pectus carinatum and 11.1% (1/9) spinal stenosis. Coronary artery disease was present in 53.8% (7/13), and 30.8% (4/13) patients previously suffered a myocardial infarction. Of the eight patients who underwent cardiac surgery, 37.5% (3/8) underwent multivessel coronary artery bypass grafting, 37.5% (3/8) underwent aortic valve replacement, 25.0% (2/8) underwent type A aortic dissection repair, and the remaining 12.5% (1/8) underwent pulmonary thromboendarterectomy. Six patients underwent percutaneous intervention. Median cardiopulmonary bypass time was 136.5 [110.0, 178.8] minutes. Median arterial cannula size was 20.0 [20.0, 24.0] Fr. Bicaval cannulation was performed in all cases describing cannulation strategy (5/5). Median superior vena cava cannula size was 28.0 [28.0, 28.0] Fr, and inferior vena cava cannula size was 28.0 [28.0, 28.0] Fr. No mortality was reported with a median follow up time of 6.0 [6.0, 10.5] months. In conclusion, Common cardiac procedures can be performed with reasonable safety in this patient population. Operative adjustments may need to be made with respect to equipment to accommodate patient-specific needs.

Growing up different in Neolithic China: A contextualised case study and differential diagnosis of a young adult with skeletal dysplasia

This paper presents a case study of a young adult from the late Neolithic Yangshao cultural period site (∼3300-2900 years BC) of Guanjia () located in Henan Province on the Central Plains of China, who has evidence for skeletal dysplasia characterised by proportional stunting of the long bones and a small axial skeleton, generalised osteopenia, and non-fusion of epiphyses. We provide a detailed differential diagnosis of skeletal dysplasia with paediatric onset and conclude that this is likely a form of hypopituitarism or hypothyroidism, an extremely rare finding within the archaeological context. This paper highlights the issues of distinguishing the forms of proportional dwarfism in palaeopathology because of the considerable variation in manifestation of these conditions. Finally, we assess whether there were any health and social implications for this person and community through the consideration of a bioarchaeology of care approach across the lifecourse, burial context, and information on social perceptions of 'difference' in the community. ：： （3300～2900）。，，，，。，，。。，。，、、""，。.

Severe achondroplasia due to two de novo variants in the transmembrane domain of FGFR3 on the same allele: A case report

Background

Achondroplasia (ACH), the most common form of short‐limbed skeletal dysplasia, is caused by gain‐of‐function mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. More than 97% of patients result from a heterozygous p.G380R mutation in the FGFR3 gene. We present here a child who had two de novo variants in the FGFR3 on the same allele, a common p.G380R mutation and a novel p.S378N variant.

Methods

A 3‐year‐old Japanese girl born from non‐consanguineous healthy parents showed more severe clinical and radiological phenotypes than classic ACH, including severe short‐limbed short stature with marked ossification defects in the metaphysis and epiphysis, hydrocephalus and cervicomedullary compression due to foramen magnum stenosis, prolonged pulmonary hypoplasia, and significant delay in the gross motor development. Genomic DNA was extracted from the proband and whole‐exome sequencing was performed. The variants were subsequently confirmed by Sanger sequencing.

Results

Mutation analysis demonstrated that the proband had p.S378N (c.1133G>A) and p.G380R (c.1138G>A) variants in the FGFR3 gene. Both variants were not detected in her parents and therefore considered de novo. An allele‐specific PCR was developed in order to determine whether these mutations were on the same allele (cis) or on different alleles (trans). The c.1138G>A mutation was found in the PCR product generated with the primer for the mutant 1133A, but it was not detected in the product with the wild‐type 1133G, confirming that p.S378N and p.G380R variants were located on the same allele (cis).

Conclusion

This is the second case who had two FGFR3 variants in the transmembrane domain on the same allele. The p.S378N variant may provide an additive effect on the activating receptor with the p.G380R mutation and alter the protein function, which could be responsible for the severe phenotype of the present case.

Clinical Practice Guidelines for Achondroplasia

Achondroplasia (ACH) is a skeletal dysplasia that presents with limb shortening, short stature, and characteristic facial configuration. ACH is caused by mutations of the FGFR3 gene, leading to constantly activated FGFR3 and activation of its downstream intracellular signaling pathway. This results in the suppression of chondrocyte differentiation and proliferation, which in turn impairs endochondral ossification and causes short-limb short stature. ACH also causes characteristic clinical symptoms, including foramen magnum narrowing, ventricular enlargement, sleep apnea, upper airway stenosis, otitis media, a narrow thorax, spinal canal stenosis, spinal kyphosis, and deformities of the lower extremities. Although outside Japan, papers on health supervision are available, they are based on reports and questionnaire survey results. Considering the scarcity of high levels of evidence and clinical guidelines for patients with ACH, clinical practical guidelines have been developed to assist both healthcare professionals and patients in making appropriate decisions in specific clinical situations. Eleven clinical questions were established and a systematic literature search was conducted using PubMed/MEDLINE. Evidence-based recommendations were developed, and the guidelines describe the recommendations related to the clinical management of ACH. We anticipate that these clinical practice guidelines for ACH will be useful for healthcare professionals and patients alike.

Successful Mechanical Thrombectomy Using Solumbra Technique In a 35-year-old Man With Achondroplasia: a case report

Background

Achondroplasia is one of the most common types of dwarfism and is inherited as an autosomal dominant disease. The patients with achondroplasia suffer from various complications such as craniofacial, central nervous system, spinal, respiratory and cardiac anomalies.

Case Description

We report a case of a 35-year-old man with achondroplasia who visited the emergency room with right hemiplegia and aphasia within 6 hours after onset. An Initial CT angiography showed the total occlusion of a left internal cerebral artery due to the thrombus. We treated the patient with endovascular thrombectomy using “Solumbra technique” with balloon guiding catheter. The procedure was successful and result was completely recanalized with Thrombolysis in Cerebral Infarction (TICI) scale 3 and the weakness also improved from grade II to grade IV.

Conclusion

Acute ischemic stroke patients with achondroplasia could be treated with mechanical thrombectomy.