European Achondroplasia Forum Practical Considerations for Following Adults with Achondroplasia

Achondroplasia is a lifelong condition requiring lifelong management. There is consensus that infants and children with achondroplasia should be managed by a multidisciplinary team experienced in the condition. However, many people are lost to follow-up after the transition from paediatric to adult care, and there is no standardised approach for management in adults, despite the recent availability of international consensus guidelines. To address this, the European Achondroplasia Forum has developed a patient-held checklist to support adults with achondroplasia in managing their health. The checklist highlights key symptoms of spinal stenosis and obstructive sleep apnoea, both among the most frequent and potentially severe medical complications in adults with achondroplasia. The checklist acts as a framework to support individuals and their primary care provider in completing a routine review. General advice on issues such as blood pressure, pain, hearing, weight, adaptive aids, and psychosocial aspects are also included. The checklist provides key symptoms to be aware of, in addition to action points so that people can approach their primary care provider and be directed to the appropriate specialist, if needed. Additionally, the European Achondroplasia Forum offers some ideas on implementing the checklist during the transition from paediatric to adult care, thus ensuring the existing multidisciplinary team model in place during childhood can support in engaging individuals and empowering them to take responsibility for their own care as they move into adulthood.

A scoping review of nutrition issues and management strategies in individuals with skeletal dysplasia

PURPOSE

Skeletal dysplasia are heterogeneous conditions affecting the skeleton. Common nutrition issues include feeding difficulties, obesity, and metabolic complications. This systematic scoping review aimed to identify key nutrition issues, management strategies, and gaps in knowledge regarding nutrition in skeletal dysplasia.

METHODS

The databases Ovid MEDLINE, Ovid EMBASE, Ebsco CINAHL, Scopus, and Cochrane Central Register of Controlled Trials and Database of Systematic Reviews were searched. Reference lists and citing literature for included studies were searched. Eligible studies included participants with skeletal dysplasia and described: anthropometry, body composition, nutrition-related biochemistry, clinical issues, dietary intake, measured energy or nutrition requirements, or nutrition interventions.

RESULTS

The literature search identified 8509 references from which 138 studies were included (130 observational, 3 intervention, 2 systematic reviews, and 3 clinical guidelines). Across 17 diagnoses identified, most studies described osteogenesis imperfecta (n = 50) and achondroplasia or hypochondroplasia (n = 47). Nutrition-related clinical issues, biochemistry, obesity, and metabolic complications were most commonly reported, and few studies measured energy requirements (n = 5).

CONCLUSION

Nutrition-related comorbidities are documented in skeletal dysplasia; yet, evidence to guide management is scarce. Evidence describing nutrition in rarer skeletal dysplasia conditions is lacking. Advances in skeletal dysplasia nutrition knowledge is needed to optimize broader health outcomes.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

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

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

Pharmacokinetics and Exposure-Response of Vosoritide in Children with Achondroplasia

BACKGROUND AND OBJECTIVE

Vosoritide, an analog of C-type natriuretic peptide, has been developed for the treatment of children with achondroplasia. The pharmacokinetics of vosoritide and relationships between plasma exposure and efficacy, biomarkers, and safety endpoints were evaluated in a phase II, open-label, dose-escalation study (N = 35 patients aged 5-14 years who received daily subcutaneous injections for 24 months) and a phase III, double-blind, placebo-controlled study (N = 60 patients aged 5-18 years randomized to receive daily subcutaneous injections for 52 weeks).

METHODS

Pharmacokinetic parameters for both studies were obtained from non-compartmental analysis. Potential correlations between vosoritide exposure and changes in annualized growth velocity, collagen type X marker (CXM; a biomarker of endochondral ossification), cyclic guanosine monophosphate (cGMP; a biomarker of pharmacological activity), heart rate, and systolic and diastolic blood pressures were then evaluated.

RESULTS

The exposure-response relationships for changes in both annualized growth velocity and the CXM biomarker saturated at 15 μg/kg, while systemic pharmacological activity, as measured by urinary cGMP, was near maximal or saturated at exposures obtained at the highest dose studied (i.e. 30 μg/kg). This suggested that the additional bioactivity was likely in tissues not related to endochondral bone formation. In the phase III study, following subcutaneous administration at the recommended dose of 15 μg/kg to patients with achondroplasia aged 5-18 years, vosoritide was rapidly absorbed with a median time to maximal plasma concentration (C_max) of 15 minutes, and cleared with a mean half-life of 27.9 minutes after 52 weeks of treatment. Vosoritide exposure (C_max and area under the concentration-time curve [AUC]) was consistent across visits. No evidence of accumulation with once-daily dosing was observed. Total anti-vosoritide antibody (TAb) responses were detected in the serum of 25 of 60 (42%) treated patients in the phase III study, with no apparent impact of TAb development noted on annualized growth velocity or vosoritide exposure. Across the exposure range obtained with 15 µg/kg in the phase III study, no meaningful correlations between vosoritide plasma exposure and changes in annualized growth velocity or CXM, or changes from predose heart rate, and systolic or diastolic blood pressures were observed.

CONCLUSIONS

The results support the recommended dose of vosoritide 15 µg/kg for once-daily subcutaneous administration in patients with achondroplasia aged ≥ 5 years whose epiphyses are not closed.

CLINICAL TRIALS REGISTRATION

NCT02055157, NCT03197766, and NCT01603095.

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.

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

Achondroplasia, the most common form of disproportionate short stature, is caused by a variant in the fibroblast growth factor receptor 3 (FGFR3) gene. Advances in drug treatment for achondroplasia have underscored the need to better understand the natural history of this condition. This article provides a critical review and discussion of the natural history of achondroplasia based on current literature evidence and the perspectives of clinicians with extensive knowledge and practical experience in managing individuals with this diagnosis. This review draws evidence from recent and ongoing longitudinal natural history studies, supplemented with relevant cross-sectional studies where longitudinal research is lacking, to summarize the current knowledge on the nature, incidence, chronology, and interrelationships of achondroplasia-related comorbidities across the lifespan. When possible, data related to adults are presented separately from data specific to children and adolescents. Gaps in knowledge regarding clinical care are identified and areas for future research are recommended and discussed.

Obesity in achondroplasia patients: from evidence to medical monitoring

Achondroplasia is a rare genetic disease representing the most common form of short-limb dwarfism. It is characterized by bone growth abnormalities that are well characterized and by a strong predisposition to abdominal obesity for which causes are unknown. Despite having aroused interest at the end of the 20 h century, there are still only very little data available on this aspect of the pathology. Today, interest is rising again, and some studies are now proposing mechanistic hypotheses and guidance for patient management. These data confirm that obesity is a major health problem in achondroplasia necessitating an early yet complex clinical management. Anticipatory care should be directed at identifying children who are at high risk to develop obesity and intervening to prevent the metabolic complications in adults. In this review, we are regrouping available data characterizing obesity in achondroplasia and we are identifying the current tools used to monitor obesity in these patients.