Mutations in fibroblast growth-factor receptor 3 in sporadic cases of achondroplasia occur exclusively on the paternally derived chromosome

Craniofacial syndromes and class III phenotype: common genotype fingerprints? A scoping review and meta-analysis

Skeletal Class III (SCIII) is among the most challenging craniofacial dysmorphologies to treat. There is, however, a knowledge gap regarding which syndromes share this clinical phenotype. The aims of this study were to: (i) identify the syndromes affected by the SCIII phenotype; (ii) clarify the involvement of maxillary and/or mandibular structures; (iii) explore shared genetic/molecular mechanisms. A two-step strategy was designed: [Step#1] OMIM, MHDD, HPO, GeneReviews and MedGen databases were explored; [Step#2]: Syndromic conditions indexed in [Step#1] were explored in Medline, Pubmed, Scopus, Cochrane Library, WOS and OpenGrey. Eligibility criteria were defined. Individual studies were assessed for risk of bias using the New Ottawa Scale. For quantitative analysis, a meta-analysis was conducted. This scoping review is a hypothesis-generating research. Twenty-two studies met the eligibility criteria. Eight syndromes affected by the SCIII were targeted: Apert syndrome, Crouzon syndrome, achondroplasia, X-linked hypohidrotic ectodermal dysplasia (XLED), tricho-dento-osseous syndrome, cleidocranial dysplasia, Klinefelter and Down syndromes. Despite heterogeneity between studies [p < 0.05], overall effects showed that midface components were affected in Apert and Down Syndromes, lower face in Klinefelter Syndrome and midface and lower face components in XLED. Our review provides new evidence on the craniofacial characteristics of genetically confirmed syndromes exhibiting the SCIII phenotype. Four major regulatory pathways might have a modulatory effect on this phenotype. IMPACT: What does this review add to the existing literature? To date, there is no literature exploring which particular syndromes exhibit mandibular prognathism as a common trait. Through this research, it was possibly to identify the particular syndromes that share the skeletal Class III phenotype (mandibular prognathism) as a common trait highlighting the common genetic and molecular pathways between different syndromes acknowledging their impact in craniofacial development.

Parental age effects and Rett syndrome

Rett syndrome (RTT) is a progressive neurodevelopmental disorder, and pathogenic Methyl-CpG-binding Protein 2 (MECP2) variants are identified in >95% of individuals with typical RTT. Most of RTT-causing variants in MECP2 are de novo and usually on the paternally inherited X chromosome. While paternal age has been reported to be associated with increased risk of genetic disorders, it is unknown whether parental age contributes to the risk of the development of RTT. Clinical data including parental age, RTT diagnostic status, and clinical severity are collected from 1226 participants with RTT and confirmed MECP2 variants. Statistical analyses are performed using Student t-test, single factor analysis of variance (ANOVA), and multi-factor regression. No significant difference is observed in parental ages of RTT probands compared to that of the general population. A small increase in parental ages is observed in participants with missense variants compared to those with nonsense variants. When we evaluate the association between clinical severity and parental ages by multiple regression analysis, there is no clear association between clinical severity and parental ages. Advanced parental ages do not appear to be a risk factor for RTT, and do not contribute to the clinical severity in individuals with RTT.

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.

Australian guidelines for the management of children with achondroplasia

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

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.

Improvement of the sagittal alignment of the spine in patients with achondroplasia after subtrochanteric femoral lengthening

PURPOSE

Limb-lengthening surgery to treat short stature has undergone great development in recent years with the use of intramedullary telescopic nails (TIMNs). A limited number of studies have explored the impact of lower limb lengthening on the spine, though their conclusions are not consistent. The aim of this research is to analyze changes in spinopelvic sagittal alignment and balance after lower limb lengthening in achondroplastic patients.

METHODS

Prospective study of patients with achondroplasia treated with bilateral femoral lengthening using an TIMN. Different sagittal spinal and pelvic plane parameters were measured on pre- and 2 year postoperative lateral spine radiographs: cervical lordosis, thoracic kyphosis, TL junction, lumbar lordosis (LL), pelvic incidence, pelvic tilt (PT), sacral slope (SS), and sagittal vertebral axis (SVA). Similarly, information regarding the elongation procedure was recorded.

RESULTS

A total of 10 patients were included (60% male), with a median age of 13.39 (2.32) years at first surgery and a median height of 120.3 (5.75) cm. A 10 cm elongation was performed in all patients through femoral subtrochanteric osteotomy. Statistically significant changes were found in LL -15.2 (7.4-17.9)º (p = 0.028), PT 11.7 (10.3-13.4)º (p = 0.018), SS - 11.6 (- 13.4 to - 10.4)º (p = 0.018) and |SVA| - 34.3 (- 39.10 to - 1.7) mm (p = 0.043).

CONCLUSION

Bilateral lower limb lengthening in patients with achondroplasia not only increases their size, but also improves sagittal spinopelvic alignment and balance. This may be due to retroversion of the pelvis and subsequent decrease in SS and LL as a result of the increased tightness of the gluteus maximus and hamstring muscles after femoral lengthening through subtrochanteric osteotomy.

LEVEL OF EVIDENCE

II, prospective comparative cohort study, before and after intervention.

The conservation of human functional variants and their effects across livestock species

Despite the clear potential of livestock models of human functional variants to provide important insights into the biological mechanisms driving human diseases and traits, their use to date has been limited. Generating such models via genome editing is costly and time consuming, and it is unclear which variants will have conserved effects across species. In this study we address these issues by studying naturally occurring livestock models of human functional variants. We show that orthologues of over 1.6 million human variants are already segregating in domesticated mammalian species, including several hundred previously directly linked to human traits and diseases. Models of variants linked to particular phenotypes, including metabolomic disorders and height, are preferentially shared across species, meaning studying the genetic basis of these phenotypes is particularly tractable in livestock. Using machine learning we demonstrate it is possible to identify human variants that are more likely to have an existing livestock orthologue, and, importantly, we show that the effects of functional variants are often conserved in livestock, acting on orthologous genes with the same direction of effect. Consequently, this work demonstrates the substantial potential of naturally occurring livestock carriers of orthologues of human functional variants to disentangle their functional impacts.

An investigation of genetic variants that exist across human and livestock species supports the clear potential of livestock models in providing insights into the mechanisms driving human diseases and traits.

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.

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.

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

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

Exclusive Neurogenic Bladder and Fecal Incontinency in an Achondroplasic Child Successfully Treated with Lumbar Foraminal Decompression

INTRODUCTION

Achondroplasia is a genetic disorder characterized by defects in the development of endochondral bone resulting in skeletal abnormalities like stenosis of the foramen magnum and of the spine, shortened limb bones, and macrocephaly. Congenital spinal stenosis is frequent and due to premature fusion of the pedicles to the laminae.

CASE PRESENTATION

We report a case of neurogenic bladder and fecal incontinence due to lumbar stenosis successfully treated with L1-L5 partial laminectomy and foraminotomy in a 7-year-old achondroplasic child.

DISCUSSION/CONCLUSION

To our knowledge, this is the first case report of exclusive neurogenic bladder and fecal incontinence in an achondroplasic child. Neurogenic bladder and fecal incontinence without motor impairment may be early and exclusive clinical findings of lumbar stenosis in children with achondroplasia.

Advanced paternal age and risk of cancer in offspring

Many risk factors of cancer have been established, but the contribution of paternal age in this regard remains largely unexplored. To further understand the etiology of cancer, we investigated the relationship between paternal age and cancer incidence using PLCO cohort. Cox proportional hazards models were performed to assess the association between paternal age and the risk of cancers. During follow-up time (median 11.5 years), 18,753 primary cancers occurred. Paternal age was associated with reduced risk of cancers of the female genitalia (HR, 0.79; 95%CI, 0.66-0.94; P = 0.008) as well as cancers of the respiratory and intrathoracic organs (HR, 0.78; 95%CI, 0.63-0.97; P = 0.026). The association was stronger for lung cancer (HR, 0.67; 95%CI, 0.52-0.86; P = 0.002). The subgroup analysis suggested that age, gender, smoking and BMI were related to the decreased cancer incidence of the respiratory and intrathoracic organs, lung and the female genitalia. Positive linear associations were observed between paternal age and cancer incidence of the female genitalia, respiratory and intrathoracic organs and the lungs. These findings indicate that advanced paternal age is an independent protective factor against various cancers in offspring.

Typical achondroplasia secondary to a unique insertional variant of FGFR3 with in vitro demonstration of its effect on FGFR3 function

We describe an individual in whom clinical and radiographic features are typical for achondroplasia, but in whom the common variants of FGFR3 that result in achondroplasia are absent. Whole exome sequencing demonstrated a novel, de novo 6 base pair tandem duplication in FGFR3 that results in the insertion of Ser-Phe after position Leu324. in vitro studies showed that this variant results in aberrant dimerization, excessive spontaneous phosphorylation of FGFR3 dimers and excessive, ligand-independent tyrosine kinase activity. Together, these data suggest that this variant leads to constitutive disulfide bond-mediated dimerization, and that this, surprisingly, occurs to an extent similar to the neonatal lethal thanatophoric dysplasia type I Ser249Cys variant.

Novel therapeutic approaches for the treatment of achondroplasia

Achondroplasia is the most common form of human dwarfism. The molecular basis of achondroplasia was elucidated in 1994 with the identification of the fibroblast growth factor receptor 3 (FGFR3) as the causative gene. Missense mutations causing achondroplasia result in activation of FGFR3 and its downstream signaling pathways, disturbing chondrogenesis, osteogenesis, and long bone elongation. A more accurate understanding of the clinical and molecular aspects of achondroplasia has allowed new therapeutic approaches to be developed. These are based on: clear understanding of the natural history of the disease; proof-of-concept preclinical studies in mouse models; and the current state of knowledge regarding FGFR3 and related growth plate homeostatic pathways. This review provides a brief overview of the preclinical mouse models of achondroplasia that have led to new, non-surgical therapeutic strategies being assessed and applied to children with achondroplasia through pioneering clinical trials.

FGFR3 Alterations in the Era of Immunotherapy for Urothelial Bladder Cancer

FGFR3 is a prognostic and predictive marker and is a validated therapeutic target in urothelial bladder cancer. Its utility as a marker and target in the context of immunotherapy is incompletely understood. We review the role of FGFR3 in bladder cancer and discuss preclinical and clinical clues of its effectiveness as a patient selection factor and therapeutic target in the era of immunotherapy.

Noninvasive prenatal sequencing for multiple Mendelian monogenic disorders among fetuses with skeletal dysplasia or increased nuchal translucency

OBJECTIVES

To evaluate the performance of noninvasive prenatal sequencing for multiple Mendelian monogenic disorders (NIPS-M) among fetuses with skeletal abnormalities or increased nuchal translucency (NT).

METHODS

Pregnancies with fetal skeletal abnormalities or increased NT (≥3.0 mm) observed by ultrasonography were recruited between October 2017 and March 2019. Parental blood from 13 couples were collected for NIPS-M testing reported. All the NIPS-M results were followed up by invasive diagnostic testing or neonatal examination.

RESULTS

Among the 13 cases, 8 (61.5%) yielded positive results for pathogenic variants in the FGFR3, COL1A1, RAF1, PTPN11 and SOS1 genes by NIPS-M. One case was excluded for further analysis due to insufficient fetal DNA (<4.5%). De novo mutations were reported in six of the eight positive cases (75%). The other two were inconclusive as the pathogenic variants were detected in both plasma and genomic DNA of the mothers. The sensitivity of NIPS-M was 100%.

CONCLUSIONS

Our pilot study demonstrates that NIPS-M is an accurate approach for detection of multiple monogenic disorders among fetuses with skeletal abnormalities or increased NT. It serves as an alternative and highly sensitive method to provide valuable molecular information for these groups of women who are reluctant to undergo invasive procedure.

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.

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.

Clinical application of medical exome sequencing for prenatal diagnosis of fetal structural anomalies

OBJECTIVE

To evaluate the clinical application of medical exome sequencing (MES) for prenatal diagnosis of genetic diseases related to fetal structural anomalies detected by prenatal ultrasound examination.

STUDY DESIGN

A total of 105 fetuses with structural anomalies were negative results in both Quantitative fluorescent polymerase chain reaction (QF-PCR) and chromosomal microarray analysis (CMA). Then trio-based MES was further used for identifying the potential monogenic diseases in these fetuses. Coding regions and known pathogenic non-coding regions of over 4000 disease-related genes were interrogated, and variants were classified following the guidelines of American College of Medical Genetics (ACMG).

RESULTS

The 105 fetuses with structural anomalies were categorized into 12 phenotypic groups. A definitive diagnosis was achieved in 19% (20/105) of the cases, with the identification of 21 pathogenic or likely pathogenic variants in 14 genes. The proportion of patients with diagnostic genetic variants varied between the phenotypic groups, with the highest diagnostic yield in the cardiovascular abnormalities (44%), followed by the skeletal and limb abnormalities (38%) and brain structural abnormalities (25%). In addition, 12 fetuses were detected variants of unknown significance (VOUS), while the relevance of phenotypes and variants would further evaluated.

CONCLUSION

MES can identify the underlying genetic cause in fetal structural anomalies. It can further assist the management of pregnancy and genetic counseling. It was demonstrated the importance of translating prenatal MES into clinical practice.

Neurological Manifestations of Achondroplasia

PURPOSE OF REVIEW

This review is to delineate the neurological complications seen in patients with achondroplasia.

RECENT FINDINGS

As the understanding of the genetics of this disorder has advanced, the possibility of targets for intervention which might modify the development and management of the neurological complications of this disease may be identified. Achondroplasia is a hereditary short-limbed dwarfism which has been known for millennia. The genetic defect is a gain of function sequence variation in the fibroblast growth factor receptor 3 (FGFR3). This gene normally regulates (inhibits) bone growth thus the gain of function results in abnormal or excessive inhibition of growth. The resulting bone is subject to distortion and the result is that bone impinges on nervous tissue, most commonly at the foramen magnum, spinal canal, and nerve root outlet foramen. Awareness of the range of these complications will, hopefully, allow early and more effective intervention so as to ameliorate the nature and severity of the long-term effects of the neurological complications in patients with achondroplasia.

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.

From skeletal development to the creation of pluripotent stem cell-derived bone-forming progenitors

Bone has many functions. It is responsible for protecting the underlying soft organs, it allows locomotion, houses the bone marrow and stores minerals such as calcium and phosphate. Upon damage, bone tissue can efficiently repair itself. However, healing is hampered if the defect exceeds a critical size and/or is in compromised conditions. The isolation or generation of bone-forming progenitors has applicability to skeletal repair and may be used in tissue engineering approaches. Traditionally, bone engineering uses osteochondrogenic stem cells, which are combined with scaffold materials and growth factors. Despite promising preclinical data, limited translation towards the clinic has been observed to date. There may be several reasons for this including the lack of robust cell populations with favourable proliferative and differentiation capacities. However, perhaps the most pertinent reason is the failure to produce an implant that can replicate the developmental programme that is observed during skeletal repair. Pluripotent stem cells (PSCs) can potentially offer a solution for bone tissue engineering by providing unlimited cell sources at various stages of differentiation. In this review, we summarize key embryonic signalling pathways in bone formation coupled with PSC differentiation strategies for the derivation of bone-forming progenitors.This article is part of the theme issue 'Designer human tissue: coming to a lab near you'.

Fibroblast growth factors in skeletal development

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.

Achondroplasia: a comprehensive clinical review

Achondroplasia is the most common of the skeletal dysplasias that result in marked short stature (dwarfism). Although its clinical and radiologic phenotype has been described for more than 50 years, there is still a great deal to be learned about the medical issues that arise secondary to this diagnosis, the manner in which these are best diagnosed and addressed, and whether preventive strategies can ameliorate the problems that can compromise the health and well being of affected individuals. This review provides both an updated discussion of the care needs of those with achondroplasia and an exploration of the limits of evidence that is available regarding care recommendations, controversies that are currently present, and the many areas of ignorance that remain.

Co-Occurrence of Autism Spectrum Disorder and Achondroplasia

Autism spectrum disorder (ASD) and achondroplasia are common disorders on their own. However, this case of co-occurrence in the same patient has not yet been reported in literature except for a hypothesized statistical probability based on prevalence studies stating that two to five in 10 million children could have the probability of having both conditions occurring simultaneously. Achondroplasia typically presents with motor delays and difficulties that are related to musculoskeletal impairments that can affect self-care, mobility, and social cognition; however, the presence of delays in other domains of development, particularly in social communication, raises a suspicion of a co-occurring autism spectrum disorder. The content of this report reviews the common delays and difficulties seen in children with achondroplasia and those with autism spectrum disorder and describes the presence of both in the child presented in this case.

New diagnostic modalities and emerging treatments for neonatal bone disease

Bone disease in the neonatal period has often been regarded as an issue affecting premature infants, or a collection of rare and ultra-rare disorders that most neonatologists will see only once or twice each year, or possibly each decade. The emergence of targeted therapies for some of these rare disorders means that neonatologists may be faced with diagnostic dilemmas that need a rapid solution in order to access management options that did not previously exist. The diagnostic modalities available to the neonatologist have not changed a great deal in recent years; blood tests and radiographs still form the mainstays with other techniques usually reserved for research studies, but rapid access to genomic testing is emergent. This paper provides an update around diagnosis and management of bone problems likely to present to the neonatologist.

Natural history of 39 patients with Achondroplasia

OBJECTIVES

To characterize the natural history of 39 achondroplastic patients diagnosed by clinical, radiological and molecular assessments.

METHODS

Observational and retrospective study of 39 patients who were attended at a public tertiary level hospital between 1995 and 2016.

RESULTS

Diagnosis was made prenatally in 11 patients, at birth in 9 patients and within the first year of life in 13 patients. The most prevalent clinical findings were short stature, high forehead, trident hands, genu varum and macrocephaly. The most prevalent radiographic findings were rhizomelic shortening of the long bones and narrowing of the interpediculate distance of the caudal spine. There was motor developmental delay in 18 patients and speech delay in 16 patients. The most common clinical intercurrences were middle ear dysfunction, sleep apnea, limb pain and obesity from 2 to 9 years of age. One patient was large for the gestational age but did not develop obesity. One patient developed hydrocephalus at 10 years old. The current age of the patients varies from 15 months to 36 years. The molecular study performed by Sanger sequencing of the common heterozygous mutation 1138G>A in FGFR3 was positive in all patients. Four cases were inherited, and 35 were sporadic (paternal age from 19 to 66 years).

CONCLUSIONS

The diagnoses were made early based on clinical and radiographic findings. All cases were confirmed molecularly. Despite presenting a benign course, it is necessary to establish a systematic protocol for the surveillance of these patients due to the common clinical intercurrences.

Prion-like properties of disease-relevant proteins in amyotrophic lateral sclerosis

The hallmark of age-related neurodegenerative diseases is the appearance of cellular protein deposits and spreading of this pathology throughout the central nervous system. Growing evidence has shown the involvement and critical role of proteins with prion-like properties in the formation of these characteristic cellular aggregates. Prion-like domains of such proteins with their proposed function in the organization of membraneless organelles are prone for misfolding and promoting further aggregation. Spreading of these toxic aggregates between cells and across tissues can explain the progression of clinical phenotypes and pathology in a stereotypical manner, characteristic for almost every neurodegenerative disease. Here, we want to review the current evidence for the role of prion-like mechanisms in classical neurodegenerative diseases and ALS in particular. We will also discuss an intriguingly central role of the protein TDP-43 in the majority of cases of this devastating disease.

Novel and Recurrent Mutations in the FGFR3 Gene and Double Heterozygosity Cases in a Cohort of Brazilian Patients with Skeletal Dysplasia

Mutations in the fibroblast growth factor receptor 3 gene (FGFR3) cause achondroplasia (ACH), hypochondroplasia (HCH), and thanatophoric dysplasia types I and II (TDI/TDII). In this study, we performed a genetic study of 123 Brazilian patients with these phenotypes. Mutation hotspots of the FGFR3 gene were PCR amplified and sequenced. All cases had recurrent mutations related to ACH, HCH, TDI or TDII, except for 2 patients. One of them had a classical TDI phenotype but a typical ACH mutation (c.1138G>A) in combination with a novel c.1130T>C mutation predicted as being pathogenic. The presence of the second c.1130T>C mutation likely explained the more severe phenotype. Another atypical patient presented with a compound phenotype that resulted from a combination of ACH and X-linked spondyloepiphyseal dysplasia tarda (OMIM 313400). Next-generation sequencing of this patient's DNA showed double heterozygosity for a typical de novo ACH c.1138G>A mutation and a maternally inherited TRAPPC2 c.6del mutation. All mutations were confirmed by Sanger sequencing. A pilot study using high-resolution melting (HRM) technique was also performed to confirm several mutations identified through sequencing. We concluded that for recurrent FGFR3 mutations, HRM can be used as a faster, reliable, and less expensive genotyping test than Sanger sequencing.

Current Care and Investigational Therapies in Achondroplasia

PURPOSE OF REVIEW

The goal of this review is to evaluate the management options for achondroplasia, the most common non-lethal skeletal dysplasia. This disease is characterized by short stature and a variety of complications, some of which can be quite severe.

RECENT FINDINGS

Despite several attempts to standardize care, there is still no widely accepted consensus. This is in part due to absence of concrete data on the incidence of sudden unexplained death in infants with achondroplasia and the best investigation for ascertaining which individuals could benefit from foramen magnum decompression surgery. In this review, we identify the different options of care and management for the various orthopedic, neurologic, and respiratory complications. In parallel, several innovative or drug repositioning therapies are being investigated that would restore bone growth but may also prevent complications. Achondroplasia is the most common non-lethal skeletal dysplasia. It is characterized by short stature and a variety of complications, some of which can be quite severe. Despite several attempts to standardize care, there is still no widely accepted consensus. This is in part due to absence of concrete data on the incidence of sudden unexplained death in infants with achondroplasia and the best investigation for ascertaining which individuals could benefit from foramen magnum decompression surgery. In this review, we identify the different options of care and management for the various orthopedic, neurologic, and respiratory complications. In parallel, several innovative or drug repositioning therapies are being investigated that would restore bone growth but may also prevent complications.

Advanced paternal age and stillbirth rate: a nationwide register-based cohort study of 944,031 pregnancies in Denmark

Advanced paternal age has been associated with a variety of rare conditions and diseases of great public health impact. An increased number of de novo point mutations in sperm with increasing age have been suggested as a mechanism, which would likely also affect fetal viability. We examined the association between paternal age and stillbirth rate in a large nationwide cohort. We identified all pregnancies in Denmark from 1994 to 2010 carried to a gestational age of at least 22 completed weeks (n = 944,031) as registered in national registers and linked to individual register data about the parents. The hazard ratio of stillbirth according to paternal age was estimated, adjusted for maternal age in 1-year categories, year of outcome, and additionally parental educational levels. The relative rate of stillbirth (n = 4946) according to paternal age was found to be J-shaped with the highest hazard ratio for fathers aged more than 40 years when paternal age was modelled using restricted cubic splines. When modelled categorically, the adjusted hazard ratios of stillbirth were as follows: <25, 1.16 (95% confidence interval, CI 1.01-1.34); 25-29, 1.03 (95% CI 0.95-1.11); 35-39, 1.16 (95% CI 1.07-1.26); 40-44, 1.41 (95% CI 1.26-1.59); 45-49, 1.20 (95% CI 0.97-1.49); 50+, 1.58 (95% CI 1.18-2.11), compared with fathers aged 30-34 years. These estimates attenuated slightly when further adjusted for parental education. Our study showed that paternal age was associated with the relative rate of stillbirth in a J-shaped manner with the highest hazard ratios among fathers aged more than 40 years.

Achondroplasia: Development, pathogenesis, and therapy

Autosomal dominant mutations in fibroblast growth factor receptor 3 (FGFR3) cause achondroplasia (Ach), the most common form of dwarfism in humans, and related chondrodysplasia syndromes that include hypochondroplasia (Hch), severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN), and thanatophoric dysplasia (TD). FGFR3 is expressed in chondrocytes and mature osteoblasts where it functions to regulate bone growth. Analysis of the mutations in FGFR3 revealed increased signaling through a combination of mechanisms that include stabilization of the receptor, enhanced dimerization, and enhanced tyrosine kinase activity. Paradoxically, increased FGFR3 signaling profoundly suppresses proliferation and maturation of growth plate chondrocytes resulting in decreased growth plate size, reduced trabecular bone volume, and resulting decreased bone elongation. In this review, we discuss the molecular mechanisms that regulate growth plate chondrocytes, the pathogenesis of Ach, and therapeutic approaches that are being evaluated to improve endochondral bone growth in people with Ach and related conditions. Developmental Dynamics 246:291-309, 2017. © 2016 Wiley Periodicals, Inc.

Avascular Retinal Findings in a Child With Achondroplasia

The authors present clinical and angiographic findings in a 12-year-old girl with achondroplasia who presented with bilateral retinal peripheral nonperfusion and unilateral rhegmatogenous retinal detachment, which has not been previously described in achondroplasia. This report contributes incremental knowledge regarding aberrant retinal vascular phenomena observed in pediatric disease states and implicates the possible role of mutations in the FGFR3 gene in peripheral vascular abnormalities. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:272-274.].

Paternal aging and increased risk of congenital disease, psychiatric disorders, and cancer

As couples are increasingly delaying parenthood, the effect of the aging men and women on reproductive outcomes has been an area of increased interest. Advanced paternal age has been shown to independently affect the entire spectrum of male fertility as assessed by reductions in sperm quality and fertilization (both assisted and unassisted). Moreover, epidemiological data suggest that paternal age can lead to higher rates of adverse birth outcomes and congenital anomalies. Mounting evidence also suggests increased risk of specific pediatric and adult disease states ranging from cancer to behavioral traits. While disease states associated with advancing paternal age have been well described, consensus recommendations for neonatal screening have not been as widely implemented as have been with advanced maternal age.

The neuropsychological function of children with achondroplasia

The current observational study had three specific objectives: (i) to document any neuropsychological impairment in a sample of children with achondroplasia; (ii) to explore individual variability; and (iii) to determine the functional impact of any impairments. Fourteen children aged between 6 and 15 years with a medically confirmed diagnosis of achondroplasia (FGFR 3 mutation positive) underwent a comprehensive standardized neuropsychological evaluation. On average, while generally still within normal limits, significantly lower scores compared to standardized means were identified on: Full-scale IQ, verbal IQ, working memory, arithmetic, attention, executive functioning and aspects of day-to-day emotional, social, and behavioral functioning. Clinically significant levels of impairment at a group level were identified on measures of: arithmetic, attention, and executive functioning. There was variability among the group and for most measures scores ranged from impaired to within normal limits. A high percentage of children were impaired on measures of: verbal IQ, attention and executive functioning. Results of this study suggest a need for individual neuropsychological evaluation and monitoring of children with achondroplasia and suggest verbal IQ, arithmetic, attention, and executive functioning are particularly common areas of impairment. © 2016 Wiley Periodicals, Inc.

Spermatogonial Stem Cells: Implications for Genetic Disorders and Prevention

Spermatogonial stem cells (SSCs) propagate mammalian spermatogenesis throughout male reproductive life by continuously self-renewing and differentiating, ultimately, into sperm. SSCs can be cultured for long periods and restore spermatogenesis upon transplantation back into the native microenvironment in vivo. Conventionally, SSC research has been focused mainly on male infertility and, to a lesser extent, on cell reprogramming. With the advent of genome-wide sequencing technology, however, human studies have uncovered a wide range of pathogenic alleles that arise in the male germ line. A subset of de novo point mutations was shown to originate in SSCs and cause congenital disorders in children. This review describes both monogenic diseases (eg, Apert syndrome) and complex disorders that are either known or suspected to be driven by mutations in SSCs. We propose that SSC culture is a suitable model for studying the origin and mechanisms of these diseases. Lastly, we discuss strategies for future clinical implementation of SSC-based technology, from detecting mutation burden by sperm screening to gene correction in vitro.

The effect of parental age on the presence of de novo mutations - Lessons from neurofibromatosis type I

Background

Neurofibromatosis type 1 (NF1) is the most common autosomal dominant neurocutaneous disease with a prevalence of 1:2500. Approximately, 50% of the cases are sporadic. Advanced paternal age is associated with germline mutations and autosomal diseases. We aimed to use NF1 as a paradigm to study the effect of parental age on sporadic mutation rates for both advanced and younger parental ages.

Methods

The medical charts of 118 NF1 pediatric patients followed in a specialized Israeli NF1 clinic were evaluated. Thirty‐one cases were diagnosed by genetic tests and 87 by NIH clinical criteria. Sixty‐four cases (54%) had a negative family history of NF1 (sporadic cases). Data on parental ages at the time of the children's birth were compared to the national population database.

Results

Parental age of children with sporadic NF1 was higher than the general population (32.7 years vs. 30.1 years, respectively, for the mothers and 36.5 years vs. 32.6 years, respectively, for the fathers; P < 0.0001 for both groups). In contrast, the age of the mothers and the fathers in the familial cases (30.3 and 33.9 years, respectively) did not differ from the general population. Significantly, fewer fathers of the sporadic group had been 25–29 years old at their child's birth compared with fathers in the general population (7.8% vs. 21%, respectively, P = 0.009), and significantly more fathers were ≥40 years old (29.7% vs. 13.6%, respectively, P = 0.0002). Differences in maternal age between these two groups were less prominent.

Conclusion

Parents of sporadic NF1 cases are older. The risk for sporadic NF1 was lower when the fathers were younger at the time of the affected child's birth, and gradually increased with paternal age.

Whole-exome sequencing and whole genome re-sequencing for prenatal diagnosis of achondroplasia

OBJECTIVE

To investigate the feasibility of whole exome sequencing (WES) and whole genome re-sequencing (WGS) in the prenatal diagnosis of achondroplasia (ACH).

METHODS

Eleven highly suspected with ACH or hypochondroplasia (HCH) fetuses and their parents were enrolled in this study. Routine prenatal examinations were carried out in all pregnant women. WGS was performed for the detection of copy number variation (CNV). WES was conducted to determine the mutation of fibroblast growth factor receptor 3 (FGFR3) gene in one special family with rickets and dwarfism. Moreover, all subjects were performed Sanger sequencing for the screening of high frequent mutation sites in FGFR3 gene.

RESULTS

For ultrasound (US) examination, short femur was noted in all fetuses with FL less than 4SD and 2SD in 8 cases and one case compared with those of normal gestational weeks, respectively. CNV abnormality was identified in 5 cases, including heterozygous deletion in 4 cases and heterozygous duplication in one case. Among these variation, one case was acknowledged to be pathogenic, one case was identified as genomic polymorphism, while the pathogenicity remained unknown in other 3 cases. For the exome and Sanger sequencing, heterozygous mutation p.Tyr278Cys (833A>G) was noted in the fetus and husband of the special family, while homozygous c.1959+19G>A mutation was identified in another case.

CONCLUSION

Multiple sequencing technologies may provide an additional diagnostic tool and facilitates genetic counseling in the patients with ACH. Further improvement of gene sequencing should be done in the prenatal diagnosis for the mutant screening in other genes.

Fibroblast growth factor signaling in skeletal development and disease

Fibroblast growth factor (FGF) signaling pathways are essential regulators of vertebrate skeletal development. FGF signaling regulates development of the limb bud and formation of the mesenchymal condensation and has key roles in regulating chondrogenesis, osteogenesis, and bone and mineral homeostasis. This review updates our review on FGFs in skeletal development published in Genes & Development in 2002, examines progress made on understanding the functions of the FGF signaling pathway during critical stages of skeletogenesis, and explores the mechanisms by which mutations in FGF signaling molecules cause skeletal malformations in humans. Links between FGF signaling pathways and other interacting pathways that are critical for skeletal development and could be exploited to treat genetic diseases and repair bone are also explored.

Non-invasive prenatal diagnosis of achondroplasia and thanatophoric dysplasia: next-generation sequencing allows for a safer, more accurate, and comprehensive approach

Abstract

What's already known about this topic?

What does this study add?

Analysis of the clinical and molecular characteristics of a child with achondroplasia: A case report

Achondroplasia (ACH) is a hereditary dwarfism caused by the disturbed proliferation and differentiation of growth plate chondrocytes, followed by impaired endochondral bone growth. ACH is caused by mutations in the gene encoding the transmembrane receptor, fibroblast growth factor receptor 3 (FGFR3). In total, >90% of patients with ACH have a G1138A mutation in the transmembrane domain of the FGFR3 gene. Patients with ACH usually have no growth hormone (GH) deficiency. The current study presents the case of a four-year-old male with clinical manifestations suggestive of ACH, including a large head, prominent forehead, short upper arms and legs, and short hands with fingers assuming a trident position. The patient showed normal responses to GH provocation tests with L-dopa (peak GH concentration, 42.38 ng/ml) and insulin (peak GH concentration, 23.29 ng/ml during hypoglycemia), but a blunted response to a GH provocation test with arginine (peak GH concentration, 7.31 ng/ml). Furthermore, the GH concentration during exercise was low (4.8 ng/ml). Magnetic resonance imaging revealed a decreased pituitary volume. Thyroid function tests and the levels of sex hormones (follicle stimulating hormone, luteinizing hormone, estradiol, prolactin and progesterone), cortisol and adrenocorticotropic hormone were normal. A heterozygous G1138A mutation within the FGFR3 gene was detected, confirming the diagnosis of ACH. Thus, recombinant human GH therapy (0.1 IU/kg/day) was initiated. At the six-month follow-up, the height, arm span-to-height ratio and lower limb length-to-height ratio of the patient had increased, while the head circumference had decreased. The present results corroborate the finding that the G1138A mutation within FGFR3 is the most common ACH-causing mutation in different populations. GH may be beneficial in the treatment of short stature in ACH patients with subnormal GH secretion.

FGFR3 mutation frequency in 324 cases from the International Skeletal Dysplasia Registry

Fibroblast growth factor receptor 3 (FGFR3) is the only gene known to cause achondroplasia (ACH), hypochondroplasia (HCH), and thanatophoric dysplasia types I and II (TD I and TD II). A second, as yet unidentified, gene also causes HCH. In this study, we used sequencing analysis to determine the frequency of FGFR3 mutations for each phenotype in 324 cases from the International Skeletal Dysplasia Registry (ISDR). Our data suggest that there is a considerable overlap of genotype and phenotype between ACH and HCH. Thus, it is important to test for mutations found in either disorder when ACH or HCH is suspected. Only two of 29 cases with HCH did not have an identified mutation in FGFR3, much less than previously reported. We recommend testing other mutations in FGFR3, instead of just the common HCH mutation, p.Asn540Lys. The mutation frequency for TD I and TD II in the largest series of cases to date are also reported. This study provides valuable information on FGFR3 mutation frequency of four skeletal dysplasias for clinical diagnostic laboratories and clinicians.

Widening of the femoral proximal diaphysis--metaphysis angle in fetuses with achondroplasia

OBJECTIVES

It has recently been reported that fetuses with achondroplasia have a wider than expected femoral proximal diaphysis-metaphysis angle (femoral angle). The aim of this case-control study was to investigate this finding.

METHODS

Cases with confirmed achondroplasia (n = 6), small-for-gestational-age fetuses (n = 70) and a group of normal fetuses (n = 377) were included in this study. The ultrasound image of the femur was examined by two independent experienced observers blinded to the diagnosis, who measured the femoral angle. These values were converted into multiples of the expected median (MoM), after adjustment for gestational age and femur length. Prevalence of various prenatal ultrasound signs of achondroplasia was determined in affected fetuses. Intra- and interobserver agreement of measurement of femoral angle was assessed using 95% limits of agreement and kappa statistics.

RESULTS

The femoral angle can be measured accurately by ultrasound, and increases with both increasing gestational age and increasing femur length. The femoral angle-MoM was significantly higher in fetuses with achondroplasia than in the control group (1.36 vs 1.00 MoM, P < 0.001) and in the SGA group (1.36 vs 1.04 MoM, P < 0.001). It measured more than 130° in five of the six cases with achondroplasia (83.3%), which was the most consistent finding other than shortening of the long bones.

CONCLUSIONS

The femoral angle is wider in fetuses with achondroplasia. This new ultrasound sign appears promising as an additional discriminatory marker when clinicians are faced with a case of short long bones in the third trimester.

Neurologic manifestations of achondroplasia

Achondroplasia is the best described and most common form of the congenital short-limbed dwarfing conditions. Achondroplasia is apparent at birth and has a birth prevalence of 1 in 20000-30000 live-born infants. Achondroplasia is inherited as an autosomal dominant condition, although 80% of cases occur sporadically as new events in their families. Achondroplasia is caused, in virtually all of the cases, by a G380R mutation in fibroblast growth factor receptor 3 (FGFR3). Patients with achondroplasia should be evaluated by a multidisciplinary team of clinicians including geneticists, neurologists, and orthopedists, since there are numerous bony and neurological complications. The most severe complication results from craniocervical stenosis and medullary and upper spinal cord compression, which can have devastating and even lethal sequelae during early childhood. In subsequent decades, including adolescence, spinal cord and nerve compression are more prominent. The neurological complications of achondroplasia have been recognized in adults for more than a century and are attributed to bony defects, connective tissue structures, or both. Similar neurological complications are now appreciated in infants, young children, and teenagers with achondroplasia. Defective connective tissue elements in achondroplasia frequently lead to ligamentous laxity, which can aggravate the complications associated with bony stenosis. Bony abnormalities are known to cause neurological morbidity and lead to a shortened lifespan. Neurological complications associated with achondroplasia are reviewed, including recommendations for the evaluation and management of these clinical problems.

The effects of advanced paternal age on fertility

Modern societal pressures and expectations over the past several decades have resulted in the tendency for couples to delay conception. While women experience a notable decrease in oocyte production in their late thirties, the effect of age on spermatogenesis is less well described. While there are no known limits to the age at which men can father children, the effects of advanced paternal age are incompletely understood. This review summarizes the current state of knowledge regarding advanced paternal age and its implications on semen quality, reproductive success and offspring health. This review will serve as a guide to physicians in counseling men about the decision to delay paternity and the risks involved with conception later in life.

Analysis of the cephalometric pattern of Brazilian achondroplastic adult subjects

OBJECTIVE: The aim of this study was to assess the position of the cranial base, maxilla, and mandible of Brazilian achondroplastic adult subjects through cephalometric measurements of the cranio-dento-facial complex, and to compare the results to normal patterns established in literature. METHODS: Fourteen achondroplastic adult subjects were evaluated based on their radiographic cephalometric measurements, which were obtained using the tracings proposed by Downs, Steinner, Bjork, Ricketts and McNamara. Statistical comparison of the means was performed with Student's t test. RESULTS: When compared to normal patterns, the cranial base presented a smaller size in both its anterior and posterior portions, the cranial base angle was acute and there was an anterior projection of the porion; the maxilla was found to be smaller in size in both the anteroposterior and transversal directions, it was inclined anteriorly with anterior vertical excess, and retropositioned in relation to the cranial base and to the mandible; the mandible presented a normal-sized ramus, a decreased body and transverse dimension, a tendency towards vertical growth and clockwise rotation, and it was slightly protruded in relation to the cranial base and maxilla. CONCLUSION: Although we observed wide individual variation in some parameters, it was possible to identify significant differences responsible for the phenotypical characteristics of achondroplastic patients.

Selfish spermatogonial selection: evidence from an immunohistochemical screen in testes of elderly men

The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia–caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively–represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men. Previous analyses of DNA from randomly selected cadaveric testes showed that the levels of the corresponding FGFR2, FGFR3 and RET mutations exhibit very uneven spatial distributions, with localised hotspots surrounded by large mutation-negative areas. These studies imply that normal testes are mosaic for clusters of mutant cells: these clusters are predicted to have altered growth and signalling properties leading to their clonal expansion (selfish spermatogonial selection), but DNA extraction eliminates the possibility to study such processes at a tissue level. Using a panel of antibodies optimised for the detection of spermatocytic seminoma, a rare tumour of spermatogonial origin, we demonstrate that putative clonal events are frequent within normal testes of elderly men (mean age: 73.3 yrs) and can be classed into two broad categories. We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance. However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT. These findings support the concept that populations of spermatogonia in individual seminiferous tubules in the testes of older men are clonal mosaics with regard to their signalling properties and activation, thus fulfilling one of the specific predictions of selfish spermatogonial selection.

Paternal age effect mutations and selfish spermatogonial selection: causes and consequences for human disease

Advanced paternal age has been associated with an increased risk for spontaneous congenital disorders and common complex diseases (such as some cancers, schizophrenia, and autism), but the mechanisms that mediate this effect have been poorly understood. A small group of disorders, including Apert syndrome (caused by FGFR2 mutations), achondroplasia, and thanatophoric dysplasia (FGFR3), and Costello syndrome (HRAS), which we collectively term "paternal age effect" (PAE) disorders, provides a good model to study the biological and molecular basis of this phenomenon. Recent evidence from direct quantification of PAE mutations in sperm and testes suggests that the common factor in the paternal age effect lies in the dysregulation of spermatogonial cell behavior, an effect mediated molecularly through the growth factor receptor-RAS signal transduction pathway. The data show that PAE mutations, although arising rarely, are positively selected and expand clonally in normal testes through a process akin to oncogenesis. This clonal expansion, which is likely to take place in the testes of all men, leads to the relative enrichment of mutant sperm over time-explaining the observed paternal age effect associated with these disorders-and in rare cases to the formation of testicular tumors. As regulation of RAS and other mediators of cellular proliferation and survival is important in many different biological contexts, for example during tumorigenesis, organ homeostasis and neurogenesis, the consequences of selfish mutations that hijack this process within the testis are likely to extend far beyond congenital skeletal disorders to include complex diseases, such as neurocognitive disorders and cancer predisposition.