Temporal Lobe Malformations in Achondroplasia: Expanding the Brain Imaging Phenotype Associated with FGFR3-Related Skeletal Dysplasias.

Thanatophoric dysplasia, achondroplasia, and hypochondroplasia belong to the fibroblast growth factor receptor 3 (FGFR3) group of genetic skeletal disorders. Temporal lobe abnormalities have been documented in thanatophoric dysplasia and hypochondroplasia, and in 1 case of achondroplasia. We retrospectively identified 13 children with achondroplasia who underwent MR imaging of the brain between 2002 and 2015. All children demonstrated a deep transverse temporal sulcus on MR imaging. Further common neuroimaging findings were incomplete hippocampal rotation (12 children), oversulcation of the mesial temporal lobe (11 children), loss of gray-white matter differentiation of the mesial temporal lobe (5 children), and a triangular shape of the temporal horn (6 children). These appearances are very similar to those described in hypochondroplasia, strengthening the association of temporal lobe malformations in FGFR3-associated skeletal dysplasias.

Novel KDM6A (UTX) mutations and a clinical and molecular review of the X-linked Kabuki syndrome (KS2).

We describe seven patients with KDM6A (located on Xp11.3 and encodes UTX) mutations, a rare cause of Kabuki syndrome (KS2, MIM 300867) and report, for the first time, germ-line missense and splice-site mutations in the gene. We demonstrate that less than 5% cases of Kabuki syndrome are due to KDM6A mutations. Our work shows that similar to the commoner Type 1 Kabuki syndrome (KS1, MIM 147920) caused by KMT2D (previously called MLL2) mutations, KS2 patients are characterized by hypotonia and feeding difficulties during infancy and poor postnatal growth and short stature. Unlike KS1, developmental delay and learning disability are generally moderate-severe in boys but mild-moderate in girls with KS2. Some girls may have a normal developmental profile. Speech and cognition tend to be more severely affected than motor development. Increased susceptibility to infections, join laxity, heart, dental and ophthalmological anomalies are common. Hypoglycaemia is more common in KS2 than in KS1. Facial dysmorphism with KDM6A mutations is variable and diagnosis on facial gestalt alone may be difficult in some patients. Hypertrichosis, long halluces and large central incisors may be useful clues to an underlying KDM6A mutation in some patients.

Genotype and clinical care correlations in craniosynostosis: findings from a cohort of 630 Australian and New Zealand patients.

Craniosynostosis is one of the most common craniofacial disorders encountered in clinical genetics practice, with an overall incidence of 1 in 2,500. Between 30% and 70% of syndromic craniosynostoses are caused by mutations in hotspots in the fibroblast growth factor receptor (FGFR) genes or in the TWIST1 gene with the difference in detection rates likely to be related to different study populations within craniofacial centers. Here we present results from molecular testing of an Australia and New Zealand cohort of 630 individuals with a diagnosis of craniosynostosis. Data were obtained by Sanger sequencing of FGFR1, FGFR2, and FGFR3 hotspot exons and the TWIST1 gene, as well as copy number detection of TWIST1. Of the 630 probands, there were 231 who had one of 80 distinct mutations (36%). Among the 80 mutations, 17 novel sequence variants were detected in three of the four genes screened. In addition to the proband cohort there were 96 individuals who underwent predictive or prenatal testing as part of family studies. Dysmorphic features consistent with the known FGFR1-3/TWIST1-associated syndromes were predictive for mutation detection. We also show a statistically significant association between splice site mutations in FGFR2 and a clinical diagnosis of Pfeiffer syndrome, more severe clinical phenotypes associated with FGFR2 exon 10 versus exon 8 mutations, and more frequent surgical procedures in the presence of a pathogenic mutation. Targeting gene hot spot areas for mutation analysis is a useful strategy to maximize the success of molecular diagnosis for individuals with craniosynostosis.

Pregnancy in a woman with proportionate (primordial) dwarfism: a case report and literature review.

Primordial dwarfism is a rare form of severe proportionate dwarfism which poses significant challenges in pregnancy. A 27-year-old with primordial dwarfism (height 97 cm, weight 22 kg) and coexisting morbidities of familial hypercholesterolaemia and hypertension presented to our unit. Early pregnancy was complicated by difficult blood pressure control, sinus tachycardia, biochemical hyperthyroidism and insulin-requiring gestational diabetes. Delivery was indicated at 24 weeks with uncontrollable hypertension, progressive renal impairment and intrauterine growth restriction. A caesarean section was performed under general anaesthesia, resulting in the delivery of a 486 g male infant. This case highlights the difficulties of managing pregnancy in a woman with primordial dwarfism. Her limited capacity to respond to the physiological demands of pregnancy created a life-threatening situation, culminating in profound preterm birth.

Two novel germline KRAS mutations: expanding the molecular and clinical phenotype.

Noonan and Cardio-facio-cutaneous (CFC) syndromes are characterized by typical dysmorphic features, cardiac defects, short stature, variable ectodermal anomalies, and intellectual disability. Both belong to the Ras/mitogen-activated protein kinase pathway group of disorders and clinical features overlap other related conditions, notably LEOPARD and Costello syndromes. KRAS mutations account for about 2% of reported Noonan and <5% of reported CFC cases. The mutation spectrum includes recurrent missense changes clustering in particular domains of the KRAS protein and conferring gain-of-function. We report three patients from two unrelated families with novel missense KRAS mutations, p.K147E and p.Y71H. Both mutations affect a residue which is highly conserved in KRAS and other RAS isoforms. One of the families includes a mother and son pair who represent the first report of a vertically transmitted KRAS mutation. In addition, the mother and son pair had peripheral neuropathy, complicated by Charcot arthropathy in the mother. An unusual phenotypic effect of the specific KRAS mutation or a coincidence of two independent disorders may be considered. KRAS mutation-associated phenotypes appear to be subject to considerable clinical heterogeneity. All three cases highlight the challenges of clinical assessment in KRAS mutation-positive patients, and the utility of molecular testing as an adjunct to diagnosis.

Sixteen New Cases Contributing to the Characterization of Patients with Distal 22q11.2 Microduplications.

The chromosome region 22q11.2 has long been recognized to be susceptible to genomic rearrangement. More recently, this genomic instability has been shown to extend distally (involving LCR22E-H) to the commonly deleted/duplicated region. To date, 21 index cases with 'distal' 22q11.2 duplications have been reported. We report on the clinical and molecular characterization of 16 individuals with distal 22q11.2 duplications identified by DNA microarray analysis. Two of the individuals have been partly described previously. The clinical phenotype varied among the patients in this study, although the majority displayed various degrees of developmental delay and speech disturbances. Other clinical features included behavioral problems, hypotonia, and dysmorphic facial features. Notably, none of the patients was diagnosed with a congenital heart defect. We found a high degree of inherited duplications. Additional copy number changes of unclear clinical significance were identified in 5 of our patients, and it is possible that these may contribute to the phenotypic expression in these patients as has been suggested recently in a 2-hit 'digenic' model for 16p12.1 deletions. The varied phenotypic expression and incomplete penetrance observed for distal 22q11.2 duplications makes it exceedingly difficult to ascribe pathogenicity for these duplications. Given the observed enrichment of the duplication in patient samples versus healthy controls, it is likely that distal 22q11.2 duplications represent a susceptibility/risk locus for speech and mild developmental delay.

Phenotypic expansion and further characterisation of the 17q21.31 microdeletion syndrome.

BACKGROUND: The recognition of the 17q21.31 microdeletion syndrome has been facilitated by high resolution microarray technology. Recent clinical delineation of this condition emphasises a typical facial appearance, cardiac and renal defects, and speech delay in addition to intellectual disability, hypotonia and seizures. METHODS AND RESULTS: We describe 11 previously unreported patients expanding the phenotypic spectrum to include aortic root dilatation, recurrent joint subluxation, conductive hearing loss due to chronic otitis media, dental anomalies, and persistence of fetal fingertip pads. Molecular analysis of the deletions demonstrates a critical region spanning 440 kb involving either partially or wholly five genes, CRHR1, IMP5, MAPT, STH, and KIAA1267. CONCLUSION: These data have significant implications for the clinical diagnosis and management of other individuals with 17q21.31 deletions.

Detection of cryptic pathogenic copy number variations and constitutional loss of heterozygosity using high resolution SNP microarray analysis in 117 patients referred for cytogenetic analysis and impact on clinical practice.

BACKGROUND: Microarray genome analysis is realising its promise for improving detection of genetic abnormalities in individuals with mental retardation and congenital abnormality. Copy number variations (CNVs) are now readily detectable using a variety of platforms and a major challenge is the distinction of pathogenic from ubiquitous, benign polymorphic CNVs. The aim of this study was to investigate replacement of time consuming, locus specific testing for specific microdeletion and microduplication syndromes with microarray analysis, which theoretically should detect all known syndromes with CNV aetiologies as well as new ones. METHODS: Genome wide copy number analysis was performed on 117 patients using Affymetrix 250K microarrays. RESULTS: 434 CNVs (195 losses and 239 gains) were found, including 18 pathogenic CNVs and 9 identified as "potentially pathogenic". Almost all pathogenic CNVs were larger than 500 kb, significantly larger than the median size of all CNVs detected. Segmental regions of loss of heterozygosity larger than 5 Mb were found in 5 patients. CONCLUSIONS: Genome microarray analysis has improved diagnostic success in this group of patients. Several examples of recently discovered "new syndromes" were found suggesting they are more common than previously suspected and collectively are likely to be a major cause of mental retardation. The findings have several implications for clinical practice. The study revealed the potential to make genetic diagnoses that were not evident in the clinical presentation, with implications for pretest counselling and the consent process. The importance of contributing novel CNVs to high quality databases for genotype-phenotype analysis and review of guidelines for selection of individuals for microarray analysis is emphasised.

The skeletal manifestations of the congenital disorders of glycosylation.

The congenital disorders of glycosylation (CDG) are a rapidly expanding disease group with protean presentations. Specific end-organ involvement leads to significant morbidity and mortality, and the skeletal manifestations are often not appreciated, apart from the common association of osteopaenia with CDG-Ia. We performed a literature review of all documented skeletal manifestations in reported CDG patients, revealing a diverse range of skeletal phenotypes. We discuss the possible underlying mechanisms of these skeletal manifestations observed in CDG that are important and frequently under-recognized.

Growth, behavior, and clinical findings in 27 patients with Kabuki (Niikawa-Kuroki) syndrome.

This study was undertaken to document the phenotype of Kabuki (Niikawa-Kuroki) syndrome in patients from Australia and New Zealand, with particular emphasis on growth patterns, behavior, and relationship between head circumference and intellectual level. Data on 27 children and adults with Kabuki (Niikawa-Kuroki) syndrome from Australia and New Zealand were collected by questionnaire and clinical assessment. The patients ranged in age from 7 months to 36 years with a mean age of 7 years and 2 months. The mean age at diagnosis was 3(5/6) years, but in most cases, the facial phenotype was evident from infancy. The minimum birth prevalence was calculated at 1 in 86,000. Three of our patients died. Parents reported a behavior phenotype characterized by an excellent long-term memory and avoidance of eye contact. No correlation was found between head circumference and severity of intellectual disability. Eight of 14 patients over the age of 5 years were overweight or obese. Six of these eight patients had failure to thrive in infancy. One patient developed insulin-dependent diabetes mellitus in adolescence. Some individuals with Kabuki (Niikawa-Kuroki) syndrome show a characteristic growth profile with failure to thrive in infancy progressing to obesity or overweight in middle childhood or adolescence. A behavior phenotype was noted which requires further investigation. Head size is not a predictor of degree of intellectual disability.

IMAGe syndrome: a complex disorder affecting growth, adrenal and gonadal function, and skeletal development.

IMAGe syndrome (intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenita, genital abnormalities; MIM 300290) is a multisystem disorder with a broad phenotype, which, if unrecognized, may result in major and possibly life-threatening complications. Initial clinical features overlap with those of Russell-Silver syndrome (RSS) and isolated growth hormone (GH) deficiency, conditions from which it must be distinguished. We report an Australian male with adrenal hypoplasia congenita (AHC) in association with IMAGe syndrome. The patient had intrauterine growth restriction (IUGR) and dysmorphic features comprising small, low-set ears, micrognathia, bilateral cryptorchidism, micropenis, and skeletal abnormalities. Signs of adrenal insufficiency occurred at aged 4.6 years. Our patient differs from those previously described by the late onset of adrenal insufficiency and the presence of GH deficiency. IMAGe is a complex syndrome involving dysmorphic features; disorders of growth, gonadal, and adrenal function; and skeletal abnormalities.

Genetic counselling after carrier detection by newborn screening when one parent carries DeltaF508 and the other R117H.

Newborn screening (NBS) for cystic fibrosis (CF) has been carried out in Victoria, Australia since 1989. The primary screen is immunoreactive trypsinogen (IRT) followed by DeltaF508 mutation analysis. As part of this process, carrier babies are detected and their parents are routinely offered carrier testing as part of their follow up. The DeltaF508 parent is identified and the other parent has an extended mutation analysis performed in case they are also a carrier. One of the mutations in the extended analysis is R117H which is associated with a broad phenotypic range, from CF with suppurative lung disease, to no clinical disease. We present four healthy DeltaF508 carrier babies identified by our NBS service with both parents identified as carriers, one DeltaF508 and the other R117H. Owing to the variable phenotype associated with R117H we have developed an approach to this difficult genetic counselling situation. Centres offering or considering NBS for CF will need an approach to this problem.

Two further cases of Ohdo syndrome delineate the phenotypic variability of the condition.

Ohdo syndrome (MIM 249620) is a multiple malformation syndrome characterized by blepharophimosis, ptosis, dental hypoplasia, hearing impairment and intellectual disability. A wide range of dysmorphic features and congenital abnormalities have been described in cases reported as Ohdo and Ohdo-like syndromes. We report a further two cases of Ohdo syndrome, one with mild features and the other more severely affected, illustrating the phenotypic variability of the condition. A review of the literature highlights the severe phenotype associated with distinctive facial features, as seen in Case 2 in this report All cases with the severe phenotype have been sporadic. Subtelomeric FISH studies of all chromosome arms on the two cases showed no abnormality. We propose clinical criteria for the diagnosis of Ohdo syndrome and delineate features of the severe phenotype.

It's only teeth - are there limits to genetic testing?

Dental genetic disorders can cause severe social and psychological effects in affected individuals. The cost of treatment can be considerable, not only in financial terms but also in time spent during treatment. In theory it is, or will soon be, possible to use advances in molecular genetics for pre-natal testing, for selection of embryos using in vitro fertilization techniques, and for gene therapy. The questions we pose are whether these approaches are appropriate. We hope that this review will stimulate debate on these issues.

Amelogenesis imperfecta: a classification and catalogue for the 21st century.

Amelogenesis imperfecta (AI) is a collective term for a number of conditions with abnormal enamel formation. Many cases are inherited, either as an X-linked, autosomal dominant or autosomal recessive trait. Several classifications have evolved since 1945, based primarily on phenotype with the mode of inheritance being used in some systems as a secondary factor in allocating a case into a particular category. The benefits and shortcomings of these systems are reviewed. As we move into an era of establishing the molecular basis of AI we propose a robust mechanism for classification and cataloguing of the disorder which parallels systems used in medical genetics. This system is applicable to individuals and families irrespective of current or future knowledge of the molecular defect involved. We argue that this system is of more benefit to these individuals and families than previous classifications.

Molecular analysis for genetic counselling in amelogenesis imperfecta.

OBJECTIVE: To use molecular genetics to establish the mode of inheritance in a family with amelogenesis imperfecta. MATERIALS AND METHODS: The polymerase chain reaction was used to amplify exons of the amelogenin gene on the short arm of the X chromosome. RESULTS: A single base deletion mutation in exon 6 of the amelogenin gene was identified. This mutation was a single base deletion of a cytosine residue - 431delC - in codon 96 of exon 6, introducing a stop codon 30 codons downstream of the mutation in codon 126 of the exon. CONCLUSION: The firm establishment of an X-linked mode of inheritance affects the genetic counselling for this family.