Fraser syndrome without cryptophthalmos: Two cases

Fraser syndrome (MIM#219000) is an autosomal recessive disorder, characterized by the association of cryptophthtalmos, syndactyly of the four extremities, urinary tract abnormalities and laryngo-tracheal anomalies. This condition is due to homozygous or compound heterozygous mutations in the FRAS/FREM complex genes: FRAS1, FREM2 and GRIP1. Here we report two atypical cases of Fraser syndrome due to mutations in the FRAS1 gene without cryptophthalmos. The first proband had syndactyly of three extremities, bilateral nostril coloboma, dysplastic ears with bilateral conductive hearing loss, blepharophimosis and lacrimal duct abnormalities. FRAS1 sequencing identified two pathogenic compound heterozygous variants: a nonsense variant in exon 70 and a missense variant in exon 24. The second proband had membranous syndactyly of the four extremities, left renal agenesis, laryngeal and ano-rectal malformations, dysplastic ears and bilateral conductive hearing loss. FRAS1 sequencing identified a pathogenic homozygous variant in the last exon of the gene. This first description of molecularly confirmed cases with Fraser syndrome without cryptophthalmos could contribute to further delineation of the clinical spectrum of Fraser syndrome, especially for possible phenotypically milder cases. Larger cohorts are required to try to refer the hypothesis of genotype-phenotype correlation.

Wiedemann-Steiner syndrome as a major cause of syndromic intellectual disability: A study of 33 French cases

Wiedemann-Steiner syndrome (WSS) is a rare syndromic condition in which intellectual disability (ID) is associated with hypertrichosis cubiti, short stature, and characteristic facies. Following the identification of the causative gene (KMT2A) in 2012, only 31 cases of WSS have been described precisely in the literature. We report on 33 French individuals with a KMT2A mutation confirmed by targeted gene sequencing, high-throughput sequencing or exome sequencing. Patients' molecular and clinical features were recorded and compared with the literature data. On the molecular level, we found 29 novel mutations. We observed autosomal dominant transmission of WSS in 3 families and mosaicism in one family. Clinically, we observed a broad phenotypic spectrum with regard to ID (mild to severe), the facies (typical or not of WSS) and associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Hypertrichosis cubiti that was supposed to be pathognomonic in the literature was found only in 61% of our cases. This is the largest series of WSS cases yet described to date. A majority of patients exhibited suggestive features, but others were less characteristic, only identified by molecular diagnosis. The prevalence of WSS was higher than expected in patients with ID, suggesting than KMT2A is a major gene in ID.

Genetic counselling difficulties and ethical implications of incidental findings from array-CGH: a 7-year national survey

Microarray-based comparative genomic hybridization (aCGH) is commonly used in diagnosing patients with intellectual disability (ID) with or without congenital malformation. Because aCGH interrogates with the whole genome, there is a risk of being confronted with incidental findings (IF). In order to anticipate the ethical issues of IF with the generalization of new genome-wide analysis technologies, we questioned French clinicians and cytogeneticists about the situations they have faced regarding IF from aCGH. Sixty-five IF were reported. Forty corresponded to autosomal dominant diseases with incomplete penetrance, 7 to autosomal dominant diseases with complete penetrance, 14 to X-linked diseases, and 4 were heterozygotes for autosomal recessive diseases with a high prevalence of heterozygotes in the population. Therapeutic/preventive measures or genetic counselling could be argued for all cases except four. These four IF were intentionally not returned to the patients. Clinicians reported difficulties in returning the results in 29% of the cases, mainly when the question of IF had not been anticipated. Indeed, at the time of the investigation, only 48% of the clinicians used consents mentioning the risk of IF. With the emergence of new technologies, there is a need to report such national experiences; they show the importance of pre-test information on IF.

X-exome sequencing of 405 unresolved families identifies seven novel intellectual disability genes

X-linked intellectual disability (XLID) is a clinically and genetically heterogeneous disorder. During the past two decades in excess of 100 X-chromosome ID genes have been identified. Yet, a large number of families mapping to the X-chromosome remained unresolved suggesting that more XLID genes or loci are yet to be identified. Here, we have investigated 405 unresolved families with XLID. We employed massively parallel sequencing of all X-chromosome exons in the index males. The majority of these males were previously tested negative for copy number variations and for mutations in a subset of known XLID genes by Sanger sequencing. In total, 745 X-chromosomal genes were screened. After stringent filtering, a total of 1297 non-recurrent exonic variants remained for prioritization. Co-segregation analysis of potential clinically relevant changes revealed that 80 families (20%) carried pathogenic variants in established XLID genes. In 19 families, we detected likely causative protein truncating and missense variants in 7 novel and validated XLID genes (CLCN4, CNKSR2, FRMPD4, KLHL15, LAS1L, RLIM and USP27X) and potentially deleterious variants in 2 novel candidate XLID genes (CDK16 and TAF1). We show that the CLCN4 and CNKSR2 variants impair protein functions as indicated by electrophysiological studies and altered differentiation of cultured primary neurons from Clcn4(-/-) mice or after mRNA knock-down. The newly identified and candidate XLID proteins belong to pathways and networks with established roles in cognitive function and intellectual disability in particular. We suggest that systematic sequencing of all X-chromosomal genes in a cohort of patients with genetic evidence for X-chromosome locus involvement may resolve up to 58% of Fragile X-negative cases.

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.

IRF6 Screening of Syndromic and a priori Non-Syndromic Cleft Lip and Palate Patients: Identification of a New Type of Minor VWS Sign

Van der Woude syndrome (VWS), caused by dominant IRF6 mutation, is the most common cleft syndrome. In 15% of the patients, lip pits are absent and the phenotype mimics isolated clefts. Therefore, we hypothesized that some of the families classified as having non-syndromic inherited cleft lip and palate could have an IRF6 mutation. We screened in total 170 patients with cleft lip with or without cleft palate (CL/P): 75 were syndromic and 95 were a priori part of multiplex non-syndromic families. A mutation was identified in 62.7 and 3.3% of the patients, respectively. In one of the 95 a priori non-syndromic families with an autosomal dominant inheritance (family B), new insights into the family history revealed the presence, at birth, of lower lip pits in two members and the diagnosis was revised as VWS. A novel lower lip sign was observed in one individual in this family. Interestingly, a similar lower lip sign was also observed in one individual from a 2nd family (family A). This consists of 2 nodules below the lower lip on the external side. In a 3rd multiplex family (family C), a de novo mutation was identified in an a priori non-syndromic CL/P patient. Re-examination after mutation screening revealed the presence of a tiny pit-looking lesion on the inner side of the lower lip leading to a revised diagnosis of VWS. On the basis of this data, we conclude that IRF6 should be screened when any doubt rises about the normality of the lower lip and also if a non-syndromic cleft lip patient (with or without cleft palate) has a family history suggestive of autosomal dominant inheritance.

The mitochondrial DNA G13513A MELAS mutation in the NADH dehydrogenase 5 gene is a frequent cause of Leigh-like syndrome with isolated complex I deficiency

Leigh syndrome is a subacute necrotising encephalomyopathy frequently ascribed to mitochondrial respiratory chain deficiency. This condition is genetically heterogeneous, as mutations in both mitochondrial (mt) and nuclear genes have been reported. Here, we report the G13513A transition in the ND5 mtDNA gene in three unrelated children with complex I deficiency and a peculiar MRI aspect distinct from typical Leigh syndrome. Brain MRI consistently showed a specific involvement of the substantia nigra and medulla oblongata sparing the basal ganglia. Variable degrees of heteroplasmy were found in all tissues tested and a high percentage of mutant mtDNA was observed in muscle. The asymptomatic mothers presented low levels of mutant mtDNA in blood leucocytes. This mutation, which affects an evolutionary conserved amino acid (D393N), has been previously reported in adult patients with MELAS or LHON/MELAS syndromes, emphasising the clinical heterogeneity of mitochondrial DNA mutations. Since the G13513A mutation was found in 21% of our patients with Leigh syndrome and complex I deficiency (3/14), it appears that this mutation represents a frequent cause of Leigh-like syndrome, which should be systematically tested for molecular diagnosis in affected children and for genetic counselling in their maternal relatives.

[Isolated bilateral dysplasia of the hip in children]

BACKGROUND

Dysplasia epiphysealis capitis femoris is not well-known despite its relative frequency; its prognosis is difficult to predict.

POPULATION AND METHODS

Twenty children (19 boys and one girl) aged 2.5 to 7 years at diagnosis were included in the study. They had delayed capitis femoris apparition, or a fragmentation of dysplastic capitis femoris. The prognosis remained poor in 13 patients.

DISCUSSION

Most authors consider that prognosis of this disease is always favorable. We failed to find early prognostic criteria; radiological findings valuable for prognosis are only present after 3 to 6 years.

CONCLUSION

Early new imaging techniques have to be evaluated before considering impossibility to foresee the evolution.

Prenatal diagnosis of metatropic dwarfism

We present a case of prenatal diagnosis of severe metatropic dysplasia at 20 weeks' gestation. The characteristic prenatal features of this rare autosomal recessive chondrodysplasia appear to be significant dwarfism with an enlarged head and a narrow thorax associated with enlargement of the hands and feet, and the radiographic 'dumb-bell' appearance of the long bones.