Molecular Analysis of a Case of Thanatophoric Dysplasia Reveals Two de novo FGFR3 Missense Mutations located in cis.

OBJECTIVES: Thanatophoric dysplasia (TD) is the most common form of lethal skeletal dysplasia. It is primarily an autosomal dominant disorder and is characterised by macrocephaly, a narrow thorax, short ribs, brachydactyly, and hypotonia. In addition to these core phenotypic features, TD type I involves micromelia with bowed femurs, while TD type II is characterised by micromelia with straight femurs and a moderate to severe clover-leaf deformity of the skull. Mutations in the FGFR3 gene are responsible for all cases of TD reported to date. The objective of the study here was to delineate further the mutational spectrum responsible for TD. METHODS: Conventional polymerase chain reaction (PCR), allele-specific PCR, and sequence analysis were used to identify FGFR3 gene mutations in a fetus with a lethal skeletal dysplasia consistent with TD, which was detected during a routine antenatal ultrasound examination. RESULTS: In this report we describe the identification of two de novo missense mutations in cis in the FGFR3 gene (p.Asn540Lys and p.Val555Met) in a fetus displaying phenotypic features consistent with TD. CONCLUSION: This is the second description of a case of TD occurring as a result of double missense FGFR3 gene mutations, suggesting that the spectrum of mutations involved in the pathogenesis of TD may be broader than previously recognised.

A novel microdeletion syndrome at 9q21.13 characterised by mental retardation, speech delay, epilepsy and characteristic facial features.

The increased use of array-CGH and SNP-arrays for genetic diagnosis has led to the identification of new microdeletion/microduplication syndromes and enabled genotype-phenotype correlations to be made. In this study, nine patients with 9q21 deletions were investigated and compared with four previously Decipher reported patients. Genotype-phenotype comparisons of 13 patients revealed several common major characteristics including significant developmental delay, epilepsy, neuro-behavioural disorders and recognizable facial features including hypertelorism, feature-less philtrum, and a thin upper lip. The molecular investigation identified deletions with different breakpoints and of variable lengths, but the 750 kb smallest overlapping deleted region includes four genes. Among these genes, RORB is a strong candidate for a neurological phenotype. To our knowledge, this is the first published report of 9q21 microdeletions and our observations strongly suggest that these deletions are responsible for a new genetic syndrome characterised by mental retardation with speech delay, epilepsy, autistic behaviour and moderate facial dysmorphy.

A novel NR5A1 variant in an infant with elevated testosterone from an Australasian cohort of 46,XY patients with disorders of sex development.

BACKGROUND: NR5A1 loss-of-function mutations are increasingly found to be the cause of 46,XY disorders of sex development (DSD). OBJECTIVE: To determine the presence of NR5A1 mutations in an Australasian cohort of 17 46,XY DSD patients with presumed androgen insensitivity syndrome (AIS) who were negative for androgen receptor gene (AR) mutation. DESIGN: Exons 2-7 of NR5A1 were PCR amplified and sequenced. Gene expression and cellular localization studies were performed on a novel NR5A1 variant c.74A>G (p.Y25C) identified in this study. RESULTS: We identified one novel mutation, c.74A>G (p.Y25C) in a patient characterized by penoscrotal hypospadias with bifid scrotum. He had elevated testosterone and gonadotropins in early infancy. Functional analysis of p.Y25C in vitro demonstrated reduced transcriptional activation by SF-1 and partially impaired nuclear localization in a proportion of transfected human adrenal NCI-H295R cells. CONCLUSION: This is the first reported case of a DSD patient with a NR5A1 mutation and elevated testosterone levels. Our finding supports evaluation of NR5A1 mutations in 46,XY DSD patients with a range of testosterone levels.

TRPV4 related skeletal dysplasias: a phenotypic spectrum highlighted byclinical, radiographic, and molecular studies in 21 new families.

BACKGROUND: The TRPV4 gene encodes a calcium-permeable ion-channel that is widely expressed, responds to many different stimuli and participates in an extraordinarily wide range of physiologic processes. Autosomal dominant brachyolmia, spondylometaphyseal dysplasia Kozlowski type (SMDK) and metatropic dysplasia (MD) are currently considered three distinct skeletal dysplasias with some shared clinical features, including short stature, platyspondyly, and progressive scoliosis. Recently, TRPV4 mutations have been found in patients diagnosed with these skeletal phenotypes. METHODS AND RESULTS: We critically analysed the clinical and radiographic data on 26 subjects from 21 families, all of whom had a clinical diagnosis of one of the conditions described above: 15 with MD; 9 with SMDK; and 2 with brachyolmia. We sequenced TRPV4 and identified 9 different mutations in 22 patients, 4 previously described, and 5 novel. There were 4 mutation-negative cases: one with MD and one with SMDK, both displaying atypical clinical and radiographic features for these diagnoses; and two with brachyolmia, who had isolated spine changes and no metaphyseal involvement. CONCLUSIONS: Our data suggest the TRPV4 skeletal dysplasias represent a continuum of severity with areas of phenotypic overlap, even within the same family. We propose that AD brachyolmia lies at the mildest end of this spectrum and, since all cases described with this diagnosis and TRPV4 mutations display metaphyseal changes, we suggest that it is not a distinct entity but represents the mildest phenotypic expression of SMDK.

Two novel COL2A1 mutations associated with a Legg-Calvé-Perthes disease-like presentation.

BACKGROUND: Abnormal development and growth of the capital femoral epiphysis and acetabulum are associated with a wide variety of underlying etiologies, one of which is Legg-Calvé-Perthes disease. CASE DESCRIPTION: We report the cases of two children who presented with abnormal development of both hips and in whom novel mutations in the COL2A1 gene were found. These cases illustrate the importance of identifying individuals with a type II collagen abnormality, as it informs management, allows investigation for other complications, and provides the opportunity for accurate genetic counseling and consideration of other family members who might be at risk. LITERATURE REVIEW: The literature documents numerous private mutations in COL2A1 associated with diverse clinical phenotypes including bilateral hip dysplasia and premature osteoarthritis. Some of these mutations are associated with a joint-specific phenotype but few other skeletal or extraskeletal manifestations. Only careful clinical examination of children presenting with hip anomalies therefore will reveal additional findings that warrant an evaluation by a clinical geneticist. DNA mutation analysis may be useful for making a specific diagnosis and identifying other at-risk family members. PURPOSES AND CLINICAL RELEVANCE: The purpose of our report is to alert clinicians to the possibility that children who present with bilateral Perthes-like disease of the hip might have an underlying mutation in the gene encoding type II collagen. It is important to consider this in the differential diagnosis and workup of such children as it has specific prognostic, clinical, genetic counseling, and reproductive sequelae.

Another case of multiple juxtasutural hyperostoses, cervical exostoses, and fatty infiltration of myocardium.

We report on an individual affected by multiple juxtasutural cranial hyperostoses who later developed cervical spine hyperostoses with associated fusion anomalies. The propositus was not affected by a disorder of generalized overgrowth. An echocardiogram revealed areas of abnormal signal within the myocardium which were consistent with fatty infiltration on magnetic resonance imaging of the heart. We compare our case with a few previously reported cases that share phenotypic similarities but differ in some other clinical aspects. It is possible that these patients represent a phenotypic continuum resulting from a somatic mutation in an unknown gene.

Molecular analysis expands the spectrum of phenotypes associated with GLI3 mutations.

A range of phenotypes including Greig cephalopolysyndactyly and Pallister-Hall syndromes (GCPS, PHS) are caused by pathogenic mutation of the GLI3 gene. To characterize the clinical variability of GLI3 mutations, we present a subset of a cohort of 174 probands referred for GLI3 analysis. Eighty-one probands with typical GCPS or PHS were previously reported, and we report the remaining 93 probands here. This includes 19 probands (12 mutations) who fulfilled clinical criteria for GCPS or PHS, 48 probands (16 mutations) with features of GCPS or PHS but who did not meet the clinical criteria (sub-GCPS and sub-PHS), 21 probands (6 mutations) with features of PHS or GCPS and oral-facial-digital syndrome, and 5 probands (1 mutation) with nonsyndromic polydactyly. These data support previously identified genotype-phenotype correlations and demonstrate a more variable degree of severity than previously recognized. The finding of GLI3 mutations in patients with features of oral-facial-digital syndrome supports the observation that GLI3 interacts with cilia. We conclude that the phenotypic spectrum of GLI3 mutations is broader than that encompassed by the clinical diagnostic criteria, but the genotype-phenotype correlation persists. Individuals with features of either GCPS or PHS should be screened for mutations in GLI3 even if they do not fulfill clinical criteria.

New airway and swallow manifestations of Simpson-Golabi-Behmel syndrome.

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked disorder of overgrowth associated with multiple congenital malformations. We report on a child with typical facial and visceral manifestations of SGBS. In addition there were complex airway anomalies, swallow difficulties and associated bronchiectasis that have not previously been described. The case highlights the importance of comprehensive airway and swallow assessment in children with this overgrowth syndrome.

A missense mutation in ALDH18A1, encoding Delta1-pyrroline-5-carboxylate synthase (P5CS), causes an autosomal recessive neurocutaneous syndrome.

There are several rare syndromes combining wrinkled, redundant skin and neurological abnormalities. Although phenotypic overlap between conditions has suggested that some might be allelic to one another, the aetiology for many of them remains unknown. A consanguineous New Zealand Maori family has been characterised that segregates an autosomal recessive connective tissue disorder (joint dislocations, lax skin) associated with neurological abnormalities (severe global developmental delay, choreoathetosis) without metabolic abnormalities in four affected children. A genome-screen performed under a hypothesis of homozygosity by descent for an ancestral mutation, identified a locus at 10q23 (Z = 3.63). One gene within the candidate interval, ALDH18A1, encoding Delta1-pyrroline-5-carboxylate synthase (P5CS), was considered a plausible disease gene since a missense mutation had previously been shown to cause progressive neurodegeneration, cataracts, skin laxity, joint dislocations and metabolic derangement in a consanguineous Algerian family. A missense mutation, 2350C>T, was identified in ALDH18A1, which predicts the substitution H784Y. H784 is invariant across all phyla and lies within a previously unrecognised, conserved C-terminal motif in P5CS. In an in vivo assay of flux through this metabolic pathway using dermal fibroblasts obtained from an affected individual, proline and ornithine biosynthetic activity of P5CS was not affected by the H784Y substitution. These data suggest that P5CS may possess additional uncharacterised functions that affect connective tissue and central nervous system function.

Characterizing the oculoauriculofrontonasal syndrome.

Human dysmorphology syndromes are frequently defined by characteristic abnormalities in facial morphogenesis. Two such well recognized syndromes are the oculoauriculovertebral spectrum (OAVS) and frontonasal dysplasia (FND). OAVS is diagnosed on the basis of the presence of typical facial features which can include microtia, preauricular tags, hemifacial microsomia, lateral face clefting, epibulbar dermoids, and upper palpebral colobomata. FND is characterized by ocular hypertelorism, nasal clefting, and anterior cranium bifidum occultum. After the first patient was described with features of both OAVS and FND, at least a further 25 patients presenting the 'oculoauriculofrontonasal syndrome' (OAFNS) have been reported. We report on four more patients with OAFNS and review their features, together with those of the other patients reported in the medical literature. We suggest that, statistically, OAFNS is more likely to be a sporadically occurring condition rather than an inherited autosomal recessive trait, as previously suggested. We cannot, however, definitively exclude the possibility of autosomal dominant transmission. Considering the question of whether OAFNS is a part of OAVS, FND, or a distinct clinical entity, we conclude that, for the time being, OAFNS should be considered to be a distinct syndrome, to further our understanding of the aetiology of these conditions.

An unclassifiable short rib-polydactyly syndrome with acromesomelic hypomineralization and campomelia in siblings.

The short rib-polydactyly (SRP) group are lethal skeletal dysplasias with an autosomal recessive inheritance pattern that can be distinguished on radiological and histological grounds. We report on two consecutive pregnancies complicated by a SRP syndrome with acromesomelic hypomineralization and campomelia that cannot be definitely categorized, yet possesses features of this group of conditions. The skeletal changes observed in both cases included markedly shortened ribs, shortened humeri and femora, limb bowing, absent ossification of the radii, ulnae, tibiae and fibulae, as well as the bony elements of the hands and feet, hypoplastic scapulae and peritoneal calcifications. In one case, the pancreas was abnormal in shape, without a tail and the spleen was not identified. Ectopic splenic tissue and intestinal malrotation were identified and were suggestive of a laterality disorder. Whether these two cases should be considered an atypical form of SRP cannot be completely resolved at this present time and will need to wait on further progress in molecular testing.

Metatropic dysplasia: clinical and radiographic findings in 11 patients demonstrating long-term natural history.

We report on the largest long-term follow-up study in metatropic dysplasia incorporating data collected over a 37-year period. Case summaries from 11 patients are presented, ranging from 20 weeks of gestation to age 70 years, characterizing the natural history. All patients were seen through the Victorian Clinical Genetics Service and the Southern Cross Bone Dysplasia Centre. Our data lend little support for the current clinical classification of metatropic dysplasia and highlight a spectrum of severity in this rare condition, which we propose has an autosomal dominant inheritance pattern. Complications such as upper respiratory obstruction secondary to laryngo-tracheal dysfunction need to be carefully monitored for in infancy because this is a preventable cause of mortality. The progression of a thoracic kyphoscoliosis in this condition is often relentless and resistant to surgical treatment. Other causes of morbidity include cervical instability, hearing loss, and functional impairments resulting from degenerative joint deformity. Intellectual outcome in all surviving cases has been normal. Final adult heights ranged from 107 to 135 cm.

FGFR3 mutations and medial temporal lobe dysgenesis.

The authors describe a child who has hypochondroplasia due to an N540K mutation and who has medial temporal lobe dysgenesis. This association has been reported only twice before. FGFR3 is expressed in the brain during development and plays a role in hippocampal formation, and FGFR3 mutations could cause cerebral malformations in hypochondroplasia. Further neuroimaging studies of patients with hypochondroplasia and epilepsy or developmental delay may clarify the proportion of patients with hypochondroplasia with this pattern of central nervous system abnormalities.

Epiphyseal dysplasia and other skeletal anomalies in a patient with the 6p25 microdeletion syndrome.

The 6p25 microdeletion syndrome comprises the Axenfeld-Rieger eye anomaly in association with a characteristic facies, developmental delay, hearing loss, and organ malformations. Skeletal anomalies in the form of hemivertebrae, clubfeet, and other positional joint anomalies have also been described in some patients. We report on a patient with a 2.2-2.4 Mb terminal microdeletion of the short arm of chromosome 6 who in addition had abnormalities of the proximal femoral and humeral epiphyses. We suggest that an epiphyseal dysplasia may be an additional clinical component of the 6p25 microdeletion syndrome.

Frontometaphyseal dysplasia: mutations in FLNA and phenotypic diversity.

Frontometaphyseal dysplasia is an X-linked trait primarily characterized by a skeletal dysplasia comprising hyperostosis of the skull and modeling anomalies of the tubular bones. Extraskeletal features include tracheobronchial, cardiac, and urological malformations. A proportion of individuals have missense mutations or small deletions in the X-linked gene, FLNA. We report here our experience with comprehensive screening of the FLNA gene in a group of 23 unrelated probands (11 familial instances, 12 simplex cases; total affected individuals 32) with FMD. We found missense mutations leading to substitutions in the actin-binding domain and within filamin repeats 9, 10, 14, 16, 22, and 23 of filamin A in 13/23 (57%) of individuals in this cohort. Some mutations present with a male phenotype that is characterized by a severe skeletal dysplasia, cardiac, and genitourinary malformations that leads to perinatal death. Although no phenotypic feature consistently discriminates between females with FMD who are heterozygous for FLNA mutations and those in whom no FLNA mutation can be identified, there is a difference in the degree of skewing of X-inactivation between these two groups. This observation suggests that locus heterogeneity may exist for this disorder.

Greater trochanteric stippling in trisomy 7p.

Trisomy 7p is a rare condition involving partial or complete duplication of the short arm of chromosome 7. Radiological features include large fontanelles, widened sutures, dolicocephaly and asymmetrical skull. We report a new radiological finding of punctate calcifications in the region of femoral trochanters. This finding has not previously been reported with chromosome 7p duplication.

Blepharocheilodontic syndrome or lagophthalmos: a child with overlapping features.

The Blepharocheilodontic (BCD) syndrome (MIM119580) and lagophthalmos syndrome (MIM600990), have striking overlap in their clinical presentation. We describe a child with manifestations of both syndromes, supporting the proposal that the two entities represent a continuum of a wider syndrome.

Constitutional deletion of chromosome 20q in two patients affected with albright hereditary osteodystrophy.

Albright hereditary osteodystrophy (AHO) results from heterozygous inactivation of G(s)alpha, encoded by the GNAS1 locus on the distal long arm of chromosome 20. This autosomal dominant condition is characterized by short stature, obesity, shortening of the metacarpals and metatarsals, and variable mental retardation and may also include end-organ resistance to multiple hormones. Small insertions and deletions or point mutations of GNAS1 are found in approximately 80% of patients with AHO. The remainder may be accounted for by larger genomic rearrangements, but none have been reported to date. We now describe two patients with constitutional 20q deletions and features of AHO. Such deletions are rare in the published literature and have not previously been associated with AHO. Molecular genetic analysis confirmed complete deletion of GNAS1 in both patients. Parental origin could be determined in both cases and provides further support for the parent-of-origin effect on the biochemical status of patients with AHO.