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

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

Ligamentous laxity in children with achondroplasia: Prevalence, joint involvement, and implications for early intervention strategies

Achondroplasia (ACH), the most common form of skeletal dysplasia, is characterized by severe disproportionate short stature, rhizomelia, exaggerated lumbar lordosis, brachydactyly, macrocephaly with frontal bossing and midface hypoplasia. Ligamentous laxity has been reported as a striking feature of ACH, but its prevalence and characteristics have not been systematically evaluated yet. There is growing evidence that ligamentous laxity can be associated with chronic musculoskeletal problems and may affect motor development leading to abnormal developmental trajectories. This study aimed to assess the prevalence of ligamentous laxity in children with ACH through standardized tools, the Beighton scale and its modified version for preschool-age children. A total of 33 children (mean age 6.4 ± 3.2 years; age range 1-12.5 years) diagnosed with ACH by the demonstration of a pathogenic variant in the FGFR3 gene and 33 age- and sex-matched healthy controls were included in the study. Both ligamentous laxity assessment and neurological examinations were performed; medical history was also collected from caregivers. Children with ACH showed a 2 times higher risk of ligamentous laxity than the group without skeletal dysplasia (OR = 2.2; 95% CI = 1.0 to 4.7), with 55% of children meeting the diagnostic criteria for hypermobility. No significant difference in ligamentous laxity was observed between males and females. Joint involvement analysis revealed characteristic patterns, with knee hypermobility observed in 67% of patients, while rare was elbow hypermobility. Longitudinal assessments indicated a decreasing trend in ligamentous laxity scores over time, suggesting a potential decrease in hypermobility issues during adulthood. The findings of this study provide valuable insights into the prevalence and characteristics of ligamentous laxity in ACH. Implementation of standardized ligamentous laxity assessments might guide patients' follow-up and facilitate early interventions, helping to prevent pain and improve outcomes and quality of life for such patients. Further prospective studies are needed to explore the natural history of ligamentous laxity in ACH and investigate the potential impact of emerging pharmacological treatments upon hypermobility.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Achondroplasia Natural History Study (CLARITY): 60-year experience with hydrocephalus in achondroplasia from four skeletal dysplasia centers

OBJECTIVE

The objective of this study was to describe the incidence and management of hydrocephalus in patients with achondroplasia over a 60-year period at four skeletal dysplasia centers.

METHODS

The Achondroplasia Natural History Study (CLARITY) is a registry for clinical data from achondroplasia patients receiving treatment at four skeletal dysplasia centers in the US from 1957 to 2017. Data were entered and stored in a REDCap database and included surgeries with indications and complications, medical diagnoses, and radiographic information.

RESULTS

A total of 1374 patients with achondroplasia were included in this study. Of these, 123 (9%) patients underwent treatment of hydrocephalus at a median age of 14.4 months. There was considerable variation in the percentage of patients treated for hydrocephalus by center and decade of birth, ranging from 0% to 28%, although in the most recent decade, all centers treated less than 6% of their patients, with an average of 2.9% across all centers. Undergoing a cervicomedullary decompression (CMD) was a strong predictor for treatment of hydrocephalus (OR 5.8, 95% CI 3.9-8.4), although that association has disappeared in those born since 2010 (OR 1.1, 95% CI 0.2-5.7). In patients born since 1990, treatment of hydrocephalus with endoscopic third ventriculostomy (ETV) has become more common; it was used as the first line of treatment in 38% of patients in the most recent decade. Kaplan-Meier analysis suggests that a single ETV will treat hydrocephalus in roughly half of these patients.

CONCLUSIONS

While many children with achondroplasia have features of hydrocephalus with enlarged intracranial CSF spaces and relative macrocephaly, treatment of hydrocephalus in achondroplasia patients has become relatively uncommon in the last 20 years. Historically, there was a significant association between symptomatic foramen magnum stenosis and treatment of hydrocephalus, although concurrent treatment of both has fallen out of favor with the recognition that CMD alone will treat hydrocephalus in some patients. Despite good experimental data demonstrating that hydrocephalus in achondroplasia is best understood as communicating in nature, ETV appears to be reasonably successful in certain patients and should be considered an option in selected patients.

How pain affect real life of children and adults with achondroplasia: A systematic review

The clinical features of achondroplasia can cause acute self-limited pain that can evolve into chronic pain. Pain causes a low quality of life, in terms of physical, emotional, social, and school functioning in both adult and children with achondroplasia. We conducted a systematic review according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement to describe prevalence, assessment tools, causes and management strategies of pain in this rare disease. We found that shoulder and knee pain is typically referred during infancy, while knee pain is generally referred around 5-6 years of age. The prevalence of general pain in adolescence can be as high as 90%. Chronic pain in the achondroplasia population increases with age, with up to 70% of adults reporting general pain and back pain. Recognizing the multiple determinants of acute and chronic pain in patients with achondroplasia may enable physicians to better understand and manage this burden, particularly with the advent of new drugs that may modify some of the striking features of achondroplasia.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

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.

Whole-body and segmental analysis of body composition in adult males with achondroplasia using dual X-ray absorptiometry

Achondroplasia is a condition characterized by a genetic mutation affecting long bone endplate development. Current data suggests that the bone mineral content (BMC) and bone mineral density (BMD) of achondroplasic populations are below age matched individuals of average stature (controls). Due to the disproportionate limb-to-torso length compared to controls however, the lower BMC and BMD may be nullified when appropriately presented. The aim of this study was to measure whole-body and segmental body composition in adult males with achondroplasia (N = 10, 22 ±3 yrs), present data relative to whole-body and whole-limb values and compare all values to age matched controls (N = 17, 22 ±2 yrs). Dual X-ray absorptiometry (DEXA) was used to measure the in vivo mass of the whole-body and 15 segments, from which BMD, BMC, fat free mass (FFM) and body fat mass were measured. BMC of lumbar vertebrae (L1-4) was also measured and presented as a volumetric BMD (BMD_VOL). The achondroplasic group had less BMC, BMD and FFM, and more body fat mass than controls as a whole-body measure. The lower achondroplasic BMC and BMD was somewhat nullified when presented relative to whole-body and whole-limb values respectively. There was no difference in lumbar BMD_VOL between groups. Whole-body BMD measures presented the achondroplasic group as ‘osteopenic’. When relative to whole-limb measures however, achondroplasic BMD descriptions were normal. Further work is needed to create a body composition database for achondroplasic population’s, or for clinicians to present achondroplasic body composition values relative to the whole-limb.

[Achondroplasia: a pilot study on the psychosocial and medical features of a sample in Puerto Rico]

This study explores the psychological wellbeing of twenty-two (n = 22) adults with achondroplasia. The sample was composed of seven (n = 7) males and fifteen (n = 15) females between the ages of 21 and 75 (mean age = 39.6). Each individual completed four self-administered questionnaires: the Beck Depression Inventory (BDI-l), the Beck Anxiety Inventory (BAI), the Beck Hopelessness Scale (BHS), and Derogatis Symptom Check-list-90-Revisited (SCL-90-R). They also filled out a socio-demographic questionnaire. We found that 31.8% of the sample reported at least one comorbid condition such as, hypertension, diabetes, rheumatoid arthritis, asthma, scoliosis, thyroid problems, neuropathy, psoriasis, gastritis and/or sleep apnea; 32% reported mild to severe depressive symp- toms; 55% reported mild to severe symptoms associated to anxiety and 18% reported mild to severe symptoms associated with hopelessness; 22.7% reported mild to severe symptoms in at least one of the sub-scales in Derogatis Symptom Checklist-90-Revisited (SCL-90-R) particularly the obsessive-compulsive, paranoid and depressive subscales. Chi Square correlations (X2) were made to observe if there was interdependence between the socio-demographic variables and the administered tests. In general, no significant correlations were found between BDI-Il, BAI, BHS, SCL-90-R and civil status, gender, income and age. However, a significant correlation was found between age and the somatization sub-scale of the SCL-90-R (rs = 0.510, p < 0.05). Our findings suggest that this particular sample is at risk for developing psycho-medical conditions. There is a marked lack of research in Puerto Rico associated to achondroplasia. The development of preventive and cultural sensitive interventions is suggested in order to protect and treat individuals with the condition.

Mortality in achondroplasia study: a 42-year follow-up

Achondroplasia (ACH) is the most common dwarfing condition having a prevalence of 1/25,000 live births. An increase in overall mortality, age specific mortality up to age 34 years and heart disease-related mortality was first reported in a 1987 study of a large population of ACH individuals. Since this study, concern about premature death, particularly in young adults, has persisted in the ACH population. The present study was undertaken to follow-up the patterns of mortality in a more contemporaneous ACH population. The vital status of 718 ACH individuals from the original study and 75 new ACH individuals was determined through the search of two computerized mortality database. The results showed that the overall mortality and age-specific mortality at all ages remained significantly increased. Rates of death were similar across all 42 years of follow-up suggesting that higher death rates were still occurring in the contemporary ACH population. Accidental, neurological, and heart disease-related deaths were increased in adults. Heart disease-related mortality, between ages 25 and 35, was more than 10 times higher than the general population. Overall survival and the average life expectancy for this ACH population were decreased by 10 years. These results demonstrate that despite advances in the knowledge of the natural history of ACH and health care needs of this population, mortality remains significantly increased. The high rate of heart disease related deaths illustrates the need to identify risk factors in the ACH population and develop treatment interventions accordingly.

When is enlargement of the subarachnoid spaces not benign? A genetic perspective

Enlargement of the subarachnoid spaces is occasionally encountered during neuroimaging of children. This enlargement is generally regarded as a nonpathologic process that resolves uneventfully. However, there are several genetic disorders in which enlargement of the subarachnoid spaces can be an early sign, or the feature of an associated syndrome, that may aid in the underlying diagnosis. Recognizing subarachnoid space enlargement in these circumstances requires an understanding of the normal physiology of the subarachnoid space at different time points in a child's neurodevelopment. This article reviews the events shaping the subarachnoid space, both during normal physiologic maturation and in specific genetic disorders.

Laminectomies and achondroplasia: does body mass index influence surgical outcomes?

Obesity is a widespread and potentially serious health problem in individuals with achondroplasia. In addition to obesity, such individuals commonly experience lumbar spinal stenosis. Although laminectomies have long been the method of choice for thorough lumbar decompression, to the best of our knowledge, the relationship between body mass index (BMI) and surgical outcomes after laminectomy in patients with achondroplasia has not been investigated in a large patient population. Through a retrospective medical record review of the initial laminectomies of all individuals with achondroplasia at our institution for whom adequate records were available, we evaluated the influence of BMI on surgical outcomes after laminectomy via four criteria: (1) change in Rankin score; (2) change in walking distance; (3) intra-operative and post-operative complications; and (4) need for subsequent revision laminectomies. The 49 individuals (mean BMI: 31.5 kg/m(2) at the time of laminectomy) were stratified into the standard BMI categories: normal (<25 kg/m(2)), overweight (25-29.9 kg/m(2)), obese Class I (30-34.9 kg/m(2)), and a combined obese Class II (35-39.9 kg/m(2)) and obese Class III (>40 kg/m(2)). Our analysis indicated that there was no statistical difference between these groups in terms of the four criteria. When the study group was categorized into non-obese (normal weight and overweight) and obese (obese Classes I and II/III) groups, there was also no statistically significant improvement difference in terms the same four criteria. Our data suggest that obesity does not pose additional risks to laminectomy in individuals with achondroplasia.

Cervical high-intensity intramedullary lesions without spinal cord compression in achondroplasia

OBJECT

In the authors' experience, the appearance of a cervical high-intensity intramedullary (CHII) lesion on magnetic resonance (MR) images in the absence of local spinal cord compression is frequently observed in patients with achondroplasia, although it has been mentioned only sporadically in the literature. Hence, the authors conducted a retrospective study in a consecutive single-center series of patients with achondroplasia to determine the prevalence and imaging features of this entity. They also reviewed the literature.

METHODS

Cervical MR imaging studies obtained to establish diagnoses in 25 adult patients with achondroplasia and assessed at the Leiden University Medical Center after neurogenic claudication developed were evaluated for the presence of a CHII lesion. Imaging features of the lesion were described, and a literature search was performed. The CHII lesion was demonstrated in 16 of 25 adult patients with achondroplasia (64%) in the absence of local spinal cord compression. All lesions were located at the C-2 level and appeared to be confined to the gray matter. The CHII lesion was associated with local spinal cord thinning, most likely representing focal atrophy. In their literature search the authors found no description of the CHII lesion in adults, although its presence has been mentioned as a peculiarity in the pediatric achondroplastic population.

CONCLUSIONS

In this large series of adults with achondroplasia and symptomatic neurogenic claudication, a CHII lesion was frequently depicted on imaging studies, but it remains a fully explored imaging phenomenon. Its cause and clinical relevance require investigation, as does its prevalence in the general achondroplastic population.

Genu varum in achondroplasia

The etiology of genu varum in achondroplasia is the subject of much speculation. The purpose of the current study was to investigate the association between fibular overgrowth and genu varum in achondroplasia. A retrospective analysis was performed on the long-leg radiographs of 48 pediatric patients with achondroplasia. All patients were skeletally immature, and the average age was 7.7 years (range, 3-16 years). Boys were significantly more likely to have varus mechanical tibiofemoral angles than girls (Fisher exact test, P=0.038 for the right leg and P=0.008 for the left leg). The distance from the proximal and distal fibula to the proximal tibia knee and ankle joint orientation lines, respectively, was not associated with the alignment of the lower extremity. We conclude that fibular overgrowth does not correlate with the severity of genu varum.

Femoral perforation complicating contemporary uncemented hip arthroplasty

This case series reports on 4 patients in whom intraoperative penetration of the femoral cortex occurred and went unrecognized on routine postoperative radiographs. This case series highlights some important points. Femoral cortex penetration can and does occur with uncemented hip arthroplasty and is likely to occur when surgical exposure is difficult and inadequate (such as in patients with severe obesity) or some form of proximal femoral deformity exists (such as patients with achondroplasia). Extra diligence should be exercised to avoid this complication in the high-risk patients, and adequate 2-plain radiographs may need to be ordered intraoperatively if such complication is suspected.

Sleep disordered breathing in children with achondroplasia. Part 2. Relationship with craniofacial and airway morphology

We evaluated the craniofacial and airway morphology in children with achondroplasia complicated by snoring and apnea during sleep (AP group) in comparison with children with snoring and apnea during sleep without chromosomal aberrations (adenoid group) and healthy children without sleep disordered breathing or malalignment (healthy group). Lateral cephalograms in 10 children each (four males and six females) in the three groups were analyzed. When the AP and healthy groups were compared, the AP group showed significantly lower values for facial depth, nasal floor length, point A, point pog, and saddle angle (p<0.01) and significantly higher values for mandibular plane angle and gonial angle (p<0.01) regarding craniofacial morphology and significantly lower values for D-AD1, D-AD2, and upper pharynx (p<0.01) regarding airway morphology. When the AP and adenoid groups were compared, the AP group showed significantly lower values for facial depth, nasal floor length, point A, point pog, and saddle angle (p<0.01) and significantly higher values for mandibular plane angle and gonial angle (p<0.01) regarding craniofacial morphology and significantly lower values for D-AD1, D-AD2, and upper pharynx (p<0.05) regarding airway morphology. Thus, the craniofacial/airway morphology in the AP group was characterized by upper airway stenosis, a retruded position of the chin, and an increased mandibular plane angle due to partial early ossification of cranial bones, and an increased lower facial height due to an increased mandibular angle, which may tend to induce sleep snoring and apnea.

Analysis of lower extremity alignment in achondroplasia: interobserver reliability and intraobserver reproducibility

This study was designed to evaluate the reliability and reproducibility of frontal plane malalignment measurements using the mechanical axis deviation method in achondroplasia and to determine whether the patient's age has any influence on these measurements. A total of 150 anteroposterior standing radiographs of the lower extremities were randomly selected for the study. Radiographs were divided into three groups according to age: group 1, younger than 6 years of age; group 2, 6 to 10 years of age; group 3, older than 10 years of age. Interobserver agreement for the medial proximal tibial angle and the lateral distal tibial angle measurements were poor (0.32 and 0.38, respectively) in group 1, but agreement increased between observers with increasing patient age. Good to excellent intraobserver reproducibility was found in all groups, except measurement of the medial proximal tibial angle in group 1, where the results were poor (0.36). Significant measurement errors in the proximal and distal tibial joint lines are possible in children less than 6 years of age with achondroplasia.

Fibroblast growth factor receptor-3 as a therapeutic target for Achondroplasia--genetic short limbed dwarfism

Achondroplasia, the most common form of human dwarfism is a sporadic autosomal dominant condition that occurs in approximately 1:20,000 births. The major clinical outcome of Achondroplasia is attenuated growth, rhizomelic shortening of the long bones and craniofacial abnormalities. As of today there is no pharmacological treatment for Achondroplasia. Some improvement in the patients well being and daily function can be achieved by a surgical limb lengthening procedure. Growth hormone treatment seems to have only modest short term success and to lack long term benefits. Achondroplasia results from a single point mutation in Fibroblast Growth Factor Receptor 3 (FGFR3). In 97% of the patients, there is a Glycine to Arginine substitution at position 380 within the FGFR-3 transmembrane domain leading to receptor overactivation. This FGF receptor tyrosine kinase is expressed by chondrocytes in the growth plate of developing long bones and plays a crucial role in bone growth. Genetic disruption of the FGFR-3 gene in mice leads to a remarkable increase in the length of the vertebral column and long bones. This suggests that overaction of FGFR3 signaling may specifically impair chondrocyte function within the epiphyseal growth plates and cause Achondroplasia. Reconstituted normal bone growth may therefore be achieved by attenuation of FGFR3 signaling in the appropriate cells within the growth plate. It is highly conceivable that drug development strategies aimed either towards blocking extracellular ligand binding or towards intracellular checkpoints along the FGF signal transduction cascade, may prove successful in the treatment of Achondroplasia. This review focuses on the possible approaches for developing a drug for Achondroplasia and related skeletal disorders, using chemical, biochemical and molecular strategies.

[From gene to disease; achondroplasia and other skeletal dysplasias due to an activating mutation in the fibroblast growth factor]

Achondroplasia, the most common and best known skeletal dysplasia, is inherited in an autosomal dominant fashion. Like a number of other skeletal dysplasias, among which hypochondroplasia and thanatophoric dysplasia, achondroplasia is caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. FGFR3 is a negative regulator of bone growth. Binding of fibroblast growth factors to the FGFR3 receptor stimulates its tyrosine kinase activity in the cell. This activates a signal transduction pathway that regulates enchondral ossification by inhibition of cell division and stimulation of cell maturation and differentiation. Mutations in the FGFR3 gene give rise to activation of the receptor in the absence of growth factors, thus causing abnormal long bone development. Position and type of mutation in the FGFR3 gene determine the extent of overactivation and thus the severity of the skeletal abnormality.

Effect of paternal age in achondroplasia, thanatophoric dysplasia, and osteogenesis imperfecta

The paternal ages of nonfamilial cases of achondroplasia (AC) (n = 78), thanatophoric dysplasia (TD) (n = 64), and osteogenesis imperfecta (OI) (n = 106), were compared with those of matched controls, from an Italian Indagine Policentrica Italiana sulle Malformazioni Congenite and a South American Estudio Colaborativo Latinoamericano de Malformaciones Congénitas series. The degree of paternal age effect on the origin of these dominant mutations differed among the three conditions. Mean paternal age was highly elevated in AC, 36.30 +/- 6.74 years in the IPIMC, and 37.19 +/- 10.53 years in the ECLAMC; less consistently elevated in TD, 33.60 +/- 7.08 years in the IPIMC, and 36.41 +/- 9.38 years in the ECLAMC; and only slightly elevated in OI in the ECLAMC, 31.15 +/- 9.25 years, but not in the IPIMC, 32.26 +/- 6.07 years. Increased maternal age or birth order in these conditions disappeared when corrected for paternal age. Approximately 50% of AC and TD cases, and only 30% of OI cases, were born to fathers above age 35 years. For AC and TD, the increase in relative incidence with paternal age fitted an exponential curve. The variability of paternal age effect in these new mutations could be due, among other reasons, to the high proportion of germ-line mosaicism in OI parents, or to the localization of the AC gene, mapped to the 4p16.3 region, in the neighborhood of an unstable DNA area.

Homozygous achondroplasia: US distinction between homozygous, heterozygous, and unaffected fetuses in the second trimester

PURPOSE

To determine if and at what gestational age prenatal ultrasonography (US) enables distinction between homozygous, heterozygous, and unaffected fetuses when both parents have heterozygous achondroplasia.

MATERIALS AND METHODS

Serial US scans of 15 fetuses at 25% risk of homozygous achondroplasia were reviewed retrospectively. Femoral growth curves were established and compared with published standards to determine the gestational age, calculated according to biparietal diameter (BPD), at which femoral length crossed below the 3rd percentile. The presence and severity of achondroplasia were determined clinically after birth.

RESULTS

Femoral length crossed the 3rd percentile at 14.0-16.5 weeks BPD age (mean, 15.6 weeks) in the four homozygous fetuses and at 18.2-26.2 weeks BPD age (mean, 21.5 weeks) in the eight heterozygous fetuses. In the three unaffected fetuses, femoral length did not cross percentiles as gestational age increased.

CONCLUSION

Establishment of a femoral growth curve in the second trimester with serial US scans enables prenatal distinction between homozygous, heterozygous, and unaffected fetuses when both parents have heterozygous achondroplasia.

The birth prevalence rates for the skeletal dysplasias

This study was undertaken to establish the prevalence rates at birth of the skeletal dysplasias that can be recognised in the perinatal period. Using the data base of the Latin-American Collaborative Study of Congenital Malformations (ECLAMC), for the years 1978 to 1983, on 349 470 births (live and stillbirths), a crude prevalence rate of 2.3/10 000 was observed. However, several indications of under-registration suggest that the real value is about twice that observed. The most frequent types of skeletal dysplasia were achondroplasia, with a prevalence rate between 0.5 and 1.5/10 000 births, the thanatophoric dysplasia/achondrogenesis group (0.2 and 0.5/10 000 births), and osteogenesis imperfecta (0.4/10 000 births). The mutation rate for autosomal dominant achondroplasia was estimated at between 1.72 and 5.57 X 10(-5) per gamete per generation.

Genetic disorders on the island of St Helena

The island of St Helena lies in the South Atlantic ocean and is isolated by distance from any land mass and by lack of a harbour or airfield. In these circumstances there could be an unusual pattern of inherited disease, and for this reason we have attempted to document the presence and frequency of genetic conditions in the population, which numbers approximately 5 500. Genetic disorders identified included autosomal dominant genu valgum, hereditary angioneurotic oedema, Christmas disease and pseudo-achondroplasia. The presence of the autosomal recessive form of retinitis pigmentosa provides a possible explanation for the occurrence of that condition in the islanders of Tristan da Cunha, since they have ancestral links with the St Helena community. The recognition of these genetic disorders in this isolated population has practical implications in terms of clinical management and the provision of medical services.

Achondroplasia and hypochondroplasia. Comments on frequency, mutation rate, and radiological features in skull and spine

An attempt was made to ascertain all the dwarfs in the State of Victoria. The incidence of achondroplasia proved to be approximately 1 in 26,000 live births in the period 1969 to 1975 when ascertainment was nearly complete. This indicates a mutation rate of 1.93 X 10(-5) per generation in this locus. Paternal age was shown to influence mutation. Ascertainment in earlier years of the study was low despite the very great effort made to find all cases. Patients with hypochondroplasia were particularly difficult to find. However, 25 cases were found for study. Overlap between hypochondroplasia and achondroplasia was found in all features except the facial appearance (which was the basis of definition). Achondroplasia was more severe in all regards, but some individuals with hypochondroplasia were very short and some had extreme degrees of spinal canal stenosis. The classical measurements used to describe the skull changes in acondroplasia failed to distinguish this condition from hypochondroplasia. More efficient indices were devised, but visual assessment of the size of the facial region compared to that of the cranial valult proved more reliable than any index. The clinical distinction based upon facial appearance remains the arbitrary basis of definition.