A novel microdeletion syndrome at 3q13.31 characterised by developmental delay, postnatal overgrowth, hypoplastic male genitals, and characteristic facial features

BACKGROUND

Congenital deletions affecting 3q11q23 have rarely been reported and only five cases have been molecularly characterised. Genotype-phenotype correlation has been hampered by the variable sizes and breakpoints of the deletions. In this study, 14 novel patients with deletions in 3q11q23 were investigated and compared with 13 previously reported patients.

METHODS

Clinical data were collected from 14 novel patients that had been investigated by high resolution microarray techniques. Molecular investigation and updated clinical information of one cytogenetically previously reported patient were also included.

RESULTS

The molecular investigation identified deletions in the region 3q12.3q21.3 with different boundaries and variable sizes. The smallest studied deletion was 580 kb, located in 3q13.31. Genotype-phenotype comparison in 24 patients sharing this shortest region of overlapping deletion revealed several common major characteristics including significant developmental delay, muscular hypotonia, a high arched palate, and recognisable facial features including a short philtrum and protruding lips. Abnormal genitalia were found in the majority of males, several having micropenis. Finally, a postnatal growth pattern above the mean was apparent. The 580 kb deleted region includes five RefSeq genes and two of them are strong candidate genes for the developmental delay: DRD3 and ZBTB20.

CONCLUSION

A newly recognised 3q13.31 microdeletion syndrome is delineated which is of diagnostic and prognostic value. Furthermore, two genes are suggested to be responsible for the main phenotype.

Stüve-Wiedemann syndrome: long-term follow-up and genetic heterogeneity

Stüve-Wiedemann syndrome (SWS, OMIM 601559) is a severe autosomal recessive condition caused by mutations in the leukemia inhibitory receptor (LIFR) gene. The main characteristic features are bowing of the long bones, neonatal respiratory distress, swallowing/sucking difficulties and dysautonomia symptoms including temperature instability often leading to death in the first years of life. We report here four patients with SWS who have survived beyond 36 months of age with no LIFR mutation. These patients have been compared with six unreported SWS survivors carrying null LIFR mutations. We provide evidence of clinical homogeneity of the syndrome in spite of the genetic heterogeneity.

Mutation update for the CSB/ERCC6 and CSA/ERCC8 genes involved in Cockayne syndrome

Cockayne syndrome is an autosomal recessive multisystem disorder characterized principally by neurological and sensory impairment, cachectic dwarfism, and photosensitivity. This rare disease is linked to mutations in the CSB/ERCC6 and CSA/ERCC8 genes encoding proteins involved in the transcription-coupled DNA repair pathway. The clinical spectrum of Cockayne syndrome encompasses a wide range of severity from severe prenatal forms to mild and late-onset presentations. We have reviewed the 45 published mutations in CSA and CSB to date and we report 43 new mutations in these genes together with the corresponding clinical data. Among the 84 reported kindreds, 52 (62%) have mutations in the CSB gene. Many types of mutations are scattered along the whole coding sequence of both genes, but clusters of missense mutations can be recognized and highlight the role of particular motifs in the proteins. Genotype-phenotype correlation hypotheses are considered with regard to these new molecular and clinical data. Additional cases of molecular prenatal diagnosis are reported and the strategy for prenatal testing is discussed. Two web-based locus-specific databases have been created to list all identified variants and to allow the inclusion of future reports (www.umd.be/CSA/ and www.umd.be/CSB/).

Molecular analysis of pericentrin gene (PCNT) in a series of 24 Seckel/microcephalic osteodysplastic primordial dwarfism type II (MOPD II) families

Microcephalic osteodysplastic primordial dwarfism type II (MOPD II, MIM 210720) and Seckel syndrome (SCKL, MIM 210600) belong to the primordial dwarfism group characterised by intrauterine growth retardation, severe proportionate short stature, and pronounced microcephaly. MOPD II is distinct from SCKL by more severe growth retardation, radiological abnormalities, and absent or mild mental retardation. Seckel syndrome is associated with defective ATR dependent DNA damage signalling. In 2008, loss-of-function mutations in the pericentrin gene (PCNT) have been identified in 28 patients, including 3 SCKL and 25 MOPDII cases. This gene encodes a centrosomal protein which plays a key role in the organisation of mitotic spindles. The aim of this study was to analyse PCNT in a large series of SCKL-MOPD II cases to further define the clinical spectrum associated with PCNT mutations. Among 18 consanguineous families (13 SCKL and 5 MOPDII) and 6 isolated cases (3 SCKL and 3 MOPD II), 13 distinct mutations were identified in 5/16 SCKL and 8/8 MOPDII including five stop mutations, five frameshift mutations, two splice site mutations, and one apparent missense mutation affecting the last base of exon 19. Moreover, we demonstrated that this latter mutation leads to an abnormal splicing with a predicted premature termination of translation. The clinical analysis of the 5 SCKL cases with PCNT mutations showed that they all presented minor skeletal changes and clinical features compatible with MOPDII diagnosis. It is therefore concluded that, despite variable severity, MOPDII is a genetically homogeneous condition due to loss-of-function of pericentrin.

Further clinical and molecular delineation of the 9q subtelomeric deletion syndrome supports a major contribution of EHMT1 haploinsufficiency to the core phenotype

BACKGROUND

The 9q subtelomeric deletion syndrome (9qSTDS) is clinically characterised by moderate to severe mental retardation, childhood hypotonia and facial dysmorphisms. In addition, congenital heart defects, urogenital defects, epilepsy and behavioural problems are frequently observed. The syndrome can be either caused by a submicroscopic 9q34.3 deletion or by intragenic EHMT1 mutations leading to haploinsufficiency of the EHMT1 gene. So far it has not been established if and to what extent other genes in the 9q34.3 region contribute to the phenotype observed in deletion cases. This study reports the largest cohort of 9qSTDS cases so far.

METHODS AND RESULTS

By a multiplex ligation dependent probe amplification (MLPA) approach, the authors identified and characterised 16 novel submicroscopic 9q deletions. Direct sequence analysis of the EHMT1 gene in 24 patients exhibiting the 9qSTD phenotype without such deletion identified six patients with an intragenic EHMT1 mutation. Five of these mutations predict a premature termination codon whereas one mutation gives rise to an amino acid substitution in a conserved domain of the protein.

CONCLUSIONS

The data do not provide any evidence for phenotype-genotype correlations between size of the deletions or type of mutations and severity of clinical features. Therefore, the authors confirm the EHMT1 gene to be the major determinant of the 9qSTDS phenotype. Interestingly, five of six patients who had reached adulthood had developed severe psychiatric pathology, which may indicate that EHMT1 haploinsufficiency is associated with neurodegeneration in addition to neurodevelopmental defect.

19q13.11 deletion syndrome: a novel clinically recognisable genetic condition identified by array comparative genomic hybridisation

BACKGROUND

Deletions of chromosome 19 have rarely been reported, with the exception of some patients with deletion 19q13.2 and Blackfan-Diamond syndrome due to haploinsufficiency of the RPS19 gene. Such a paucity of patients might be due to the difficulty in detecting a small rearrangement on this chromosome that lacks a distinct banding pattern. Array comparative genomic hybridisation (CGH) has become a powerful tool for the detection of microdeletions and microduplications at high resolution in patients with syndromic mental retardation.

METHODS AND RESULTS

Using array CGH, this study identified three interstitial overlapping 19q13.11 deletions, defining a minimal critical region of 2.87 Mb, associated with a clinically recognisable syndrome. The three patients share several major features including: pre- and postnatal growth retardation with slender habitus, severe postnatal feeding difficulties, microcephaly, hypospadias, signs of ectodermal dysplasia, and cutis aplasia over the posterior occiput. Interestingly, these clinical features have also been described in a previously reported patient with a 19q12q13.1 deletion. No recurrent breakpoints were identified in our patients, suggesting that no-allelic homologous recombination mechanism is not involved in these rearrangements.

CONCLUSIONS

Based on these results, the authors suggest that this chromosomal abnormality may represent a novel clinically recognisable microdeletion syndrome caused by haploinsufficiency of dosage sensitive genes in the 19q13.11 region.

Revisiting metatropic dysplasia: presentation of a series of 19 novel patients and review of the literature

Metatropic dysplasia (MD-OMIM: 156530 and 250600) is a rare chondrodysplasia characterized by short limbs with limitation and enlargement of joints and usually severe kyphoscoliosis, first described in 1893. Up until now, 81 other patients have been reported. The phenotypic variability of MD has led to a classification based on radiological anomalies dividing into three different types: a lethal autosomal recessive form, an autosomal recessive non-lethal form and a non-lethal autosomal dominant form with less severe radiographs manifestations and a better clinical outcome. Here, we report on clinical and radiological features of 19 novel MD patients. We describe new radiological features, including precocious calcification of hyoid and cricoid cartilage, irregular and squared-off calcaneal bones and severe hypoplasia of the anterior portion of first cervical vertebrae. In addition, the observation of an overlap between the autosomal recessive non-lethal form and the non-lethal autosomal dominant form, the rarity of sibship recurrences and the observation of vertical transmissions of MD in the literature argue in favor of an autosomal dominant mode of inheritance for all MD types. This hypothesis is reinforced by the use of the statistical single ascertainment method that rejects the hypothesis of an autosomal recessive mode of inheritance responsible for MD. Therefore, we propose that recurrence in sibs is due to gonadal mosaicism.

Mutations in cytokine receptor-like factor 1 (CRLF1) account for both Crisponi and cold-induced sweating syndromes

Crisponi syndrome is a rare autosomal recessive disorder characterized by congenital muscular contractions of facial muscles, with trismus in response to stimuli, dysmorphic features, bilateral camptodactyly, major feeding and respiratory difficulties, and access of hyperthermia leading to death in the first months of life. The overlap with Stuve-Wiedemann syndrome (SWS) is striking, but the two conditions differ in that congenital lower limb bowing is absent in Crisponi syndrome, whereas it is a cardinal feature of SWS. We report here the exclusion of the leukemia inhibitory factor receptor gene in Crisponi syndrome and the identification of homozygote or compound heterozygote cytokine receptor-like factor 1 (CRLF1) mutations in four children from three unrelated families. The four mutations were located in the immunoglobulin-like and type III fibronectin domains, and three of them predicted premature termination of translation. Using real-time quantitative polymerase chain reaction, we found a significant decrease in CRLF1 mRNA expression in patient fibroblasts, which is suggestive of a mutation-mediated decay of the abnormal transcript. CRLF1 forms a heterodimer complex with cardiotrophin-like cytokine factor 1, and this heterodimer competes with ciliary neurotrophic factor for binding to the ciliary neurotrophic factor receptor (CNTFR) complex. The identification of CRLF1 mutations in Crisponi syndrome supports the key role of the CNTFR pathway in the function of the autonomic nervous system.

[Dyggve-Melchior-Clausen syndrome, diagnostic difficulty due to it similarity to Morquio disease]

INTRODUCTION

Dyggve-Melchior-Clausen syndrome (DMCS) is a rare autosomal recessive disorder produced by mutations in the Dymeclin gene recently identified. It is characterized by the association of a progressive spondylo-epi-metaphyseal dysplasia and mental retardation ranging from mild to severe. The clinical and radiological similarities at the onset of the condition with the Morquio disease may hinder its diagnosis and no biochemical abnormality that causes it has been described as of yet.

CLINICAL CASE

An eight-year-old girl had progressive postnatal dwarfism. Platyspondyly and dysplasic epiphyses and metaphyses with biochemical studies that resembled those of Morquio's disease; however the presence of specific radiological features and mental retardation led to the diagnosis of DMCS. A missense Dym mutation in homozygosis was identified.

CONCLUSION

This entity should be known as it may be easily confused with Morquio disease. Radiological appearance of the iliac crests are very pathognomonic of DMCS. Identification of Dym gene is an important step towards the prenatal diagnosis.

A gene responsible for Ghosal hemato-diaphyseal dysplasia maps to chromosome 7q33-34

Ghosal hemato-diaphyseal dysplasia is a rare autosomal recessive disorder characterized by a progressive sclerosing diaphyseal dysplasia and refractory anemia. The pathogenesis and genetic bases of this syndrome remain hitherto unknown. We have performed a genome wide search in two inbred families originating from Algeria and Tunisia. Here, we report on the mapping of a disease gene to chromosome 7q33-34 (Zmax = 4.21 at theta = 0 at locus D7S2513) in a 3.4 Mb defined by loci D7S2560 and AC091742. Ongoing studies will hopefully lead to identification of the disease-causing gene.

Clinical, molecular, and genotype-phenotype correlation studies from 25 cases of oral-facial-digital syndrome type 1: a French and Belgian collaborative study

Oral-facial-digital syndrome type 1 (OFD1) is characterised by an X linked dominant mode of inheritance with lethality in males. Clinical features include facial dysmorphism with oral, tooth, and distal abnormalities, polycystic kidney disease, and central nervous system malformations. Large interfamilial and intrafamilial clinical variability has been widely reported, and 18 distinct mutations have been previously reported within OFD1. A French and Belgian collaborative study collected 25 cases from 16 families. OFD1 was analysed using direct sequencing and phenotype-genotype correlation was performed using chi2 test. X inactivation studies were performed on blood lymphocytes. In 11 families, 11 novel mutations, including nine frameshift, one nonsense, and one missense mutation were identified, which spanned nine different exons. A combination of our results with previously reported cases showed that the majority of mutations (65.5%) was located in exons 3, 8, 9, 13, and 16. There was phenotype-genotype correlation between (a) polycystic kidney disease and splice mutations; (b) mental retardation and mutations located in exons 3, 8, 9, 13, and 16; and (c) tooth abnormalities and mutations located in coiled coil domains. Comparing the phenotype of the families with a pathogenic mutation to families with absence of OFD1 mutation, polycystic kidneys and short stature were significantly more frequent in the group with no OFD1 mutation, whereas lingual hamartomas were significantly more frequent in the group with OFD1 mutation. Finally, an X inactivation study showed non-random X inactivation in a third of the samples. Differential X inactivation between mothers and daughters in two families with high intrafamilial variability was of particular interest. Slight phenotype-genotype correlations were established, and X inactivation study showed that skewed X inactivation could be partially involved in the pathogenesis of intrafamilial clinical variability.

Multiple mechanisms are implicated in the generation of 5q35 microdeletions in Sotos syndrome

BACKGROUND

Sotos syndrome is characterised by learning difficulties, overgrowth, and a typical facial appearance. Microdeletions at 5q35.3, encompassing NSD1, are responsible for approximately 10% of non-Japanese cases of Sotos. In contrast, a recurrent approximately 2 Mb microdeletion has been reported as responsible for approximately 50% of Japanese cases of Sotos.

METHODS

We screened 471 cases for NSD1 mutations and deletions and identified 23 with 5q35 microdeletions. We investigated the deletion size, parent of origin, and mechanism of generation in these and a further 10 cases identified from published reports. We used "in silico" analyses to investigate whether repetitive elements that could generate microdeletions flank NSD1.

RESULTS

Three repetitive elements flanking NSD1, designated REPcen, REPmid, and REPtel, were identified. Up to 18 cases may have the same sized deletion, but at least eight unique deletion sizes were identified, ranging from 0.4 to 5 Mb. In most instances, the microdeletion arose through interchromosomal rearrangements of the paternally inherited chromosome.

CONCLUSIONS

Frequency, size, and mechanism of generation of 5q35 microdeletions differ between Japanese and non-Japanese cases of Sotos. Our microdeletions were identified from a large case series with a broad range of phenotypes, suggesting that sample selection variability is unlikely as a sole explanation for these differences and that variation in genomic architecture might be a contributory factor. Non-allelic homologous recombination between REPcen and REPtel may have generated up to 18 microdeletion cases in our series. However, at least 15 cannot be mediated by these repeats, including at least seven deletions of different sizes, implicating multiple mechanisms in the generation of 5q35 microdeletions.

Array-based comparative genomic hybridisation identifies high frequency of cryptic chromosomal rearrangements in patients with syndromic autism spectrum disorders

BACKGROUND

Autism spectrum disorders (ASD) refer to a broader group of neurobiological conditions, pervasive developmental disorders. They are characterised by a symptomatic triad associated with qualitative changes in social interactions, defect in communication abilities, and repetitive and stereotyped interests and activities. ASD is prevalent in 1 to 3 per 1000 people. Despite several arguments for a strong genetic contribution, the molecular basis of a most cases remains unexplained. About 5% of patients with autism have a chromosome abnormality visible with cytogenetic methods. The most frequent are 15q11-q13 duplication, 2q37 and 22q13.3 deletions. Many other chromosomal imbalances have been described. However, most of them remain undetectable using routine karyotype analysis, thus impeding diagnosis and genetic counselling.

METHODS AND RESULTS

29 patients presenting with syndromic ASD were investigated using a DNA microarray constructed from large insert clones spaced at approximately 1 Mb intervals across the genome. Eight clinically relevant rearrangements were identified in 8 (27.5%) patients: six deletions and two duplications. Altered segments ranged in size from 1.4 to 16 Mb (2-19 clones). No recurrent abnormality was identified.

CONCLUSION

These results clearly show that array comparative genomic hybridisation should be considered to be an essential aspect of the genetic analysis of patients with syndromic ASD. Moreover, besides their importance for diagnosis and genetic counselling, they may allow the delineation of new contiguous gene syndromes associated with ASD. Finally, the detailed molecular analysis of the rearranged regions may pave the way for the identification of new ASD genes.

High incidence of SHOX anomalies in individuals with short stature

OBJECTIVE

To study the SHOX gene and the PAR1 region in individuals with short stature.

METHODS

The study involved 56 cases of dyschondrosteosis and 84 cases of idiopathic short stature (ISS). The study was designed to determine the following: the prevalence of SHOX anomalies in ISS; the frequency of Madelung deformity in individuals with SHOX anomalies; and the value of a family history of short stature in deciding whether to test for the SHOX gene.

RESULTS

54 SHOX anomalies were observed, including 42 (68%) in the dyschondrosteosis group and 12 (15%) in the ISS group. The high frequency of SHOX anomalies in the ISS group can be explained by the large proportion of boys in this group, reflecting the difficulty in diagnosing dyschondrosteosis in young boys. Clinical evidence of Madelung deformity in six parents of ISS individuals emphasised the importance of family evaluation. Among the 54 SHOX anomalies, 33 PAR1 deletions were identified encompassing the SHOX gene (62%), one partial intragenic deletion (2%), nine deletions located downstream of the SHOX gene (16%), and 11 point mutations (20%).

CONCLUSIONS

These data emphasise the value of using microsatellite markers located within and downstream of the SHOX gene.

Gorlin syndrome presenting as prenatal chylothorax in a girl

Gorlin syndrome (GS), also known as nevoid basal cell carcinoma syndrome, is a rare autosomal dominant condition with an estimated prevalence of 1:57 000. GS is associated with congenital malformations and predisposition to neoplasms. The main features observed in patients with GS are basal cell carcinomas, odontogenic keratocysts, skeletal anomalies including scoliosis and bifid ribs, palmar and plantar epidermal cysts, facial dysmorphism, and cerebral falx calcification. More than 100 other clinical manifestations have also been described in the literature including ovarian fibroma, enlarged cerebral ventricles, and lymphatic as well as chylous mesenteric cysts. The Patched (PTCH) gene is responsible for GS when mutated. Here, we report on a prenatal diagnosis of GS in a girl with a chylothorax, a previously unreported feature in GS. We discuss the clinical features observed in this family and we comment on the molecular studies that allowed us to describe a previously unreported Patched gene mutation.

Wide clinical variability among 13 new Cockayne syndrome cases confirmed by biochemical assays

Cockayne syndrome is a multi-systemic, autosomal recessive disease characterised by postnatal growth failure and progressive multi-organ dysfunction. The main clinical features are severe dwarfism (<-2 SD), microcephaly (<-3 SD), psychomotor delay, sensorial loss (cataracts, pigmentary retinopathy, and deafness), and cutaneous photosensitivity. Here, 13 new cases of Cockayne syndrome are reported, which have been clinically diagnosed and confirmed using a biochemical transcription assay. The wide clinical variability, ranging from prenatal features to normal psychomotor development, is emphasised. When cardinal features are lacking, the diagnosis of Cockayne syndrome should be considered when presented with growth retardation, microcephaly, and one of the suggesting features such as enophthalmia, limb ataxia, abnormal auditory evoked responses, or increased ventricular size on cerebral imaging.