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.

Xq28 duplication including MECP2 in six unreported affected females: what can we learn for diagnosis and genetic counselling?

Duplication of the Xq28 region, involving MECP2 (dupMECP2), has been primarily described in males with severe developmental delay, spasticity, epilepsy, stereotyped movements and recurrent infections. Carrier mothers are usually asymptomatic with an extremely skewed X chromosome inactivation (XCI) pattern. We report a series of six novel symptomatic females carrying a de novo interstitial dupMECP2, and review the 14 symptomatic females reported to date, with the aim to further delineate their phenotype and give clues for genetic counselling. One patient was adopted and among the other 19 patients, seven (37%) had inherited their duplication from their mother, including three mildly (XCI: 70/30, 63/37, 100/0 in blood and random in saliva), one moderately (XCI: random) and three severely (XCI: uninformative and 88/12) affected patients. After combining our data with data from the literature, we could not show a correlation between XCI in the blood or duplication size and the severity of the phenotype, or explain the presence of a phenotype in these females. These findings confirm that an abnormal phenotype, even severe, can be a rare event in females born to asymptomatic carrier mothers, making genetic counselling difficult in couples at risk in terms of prognosis, in particular in prenatal cases.

[The challenge for dermatologists of early APECED diagnosis]. / Diagnostic précoce du syndrome APECED : un défi pour le dermatologue.

BACKGROUND: Polyglandular auto-immune syndrome type 1 (PAS-1) or auto-immune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomal recessive disorder linked to auto-immune regulator (AIRE) gene mutations. Herein, we report the case of a 3-year-old boy with APECED emphasizing the wide phenotypic variability and the extent of skin lesions. PATIENTS AND METHODS: A 3-year-old boy with a history of auto-immune hepatitis was referred for a generalized pruriginous urticaria-like eruption present for one month. He was born to non-consanguineous parents. Cutaneous examination revealed twenty-nail dystrophy, which had been present since the age of 2 years. Both direct microscopy and culture of nail samples were negative for Candida albicans. Esophagogastroduodenoscopy revealed esophageal candidiasis. A diagnosis of APECED was suspected and subsequently confirmed by molecular analysis of the AIRE gene, which showed two mutations. No other auto-immune endocrinopathies were found. DISCUSSION: Our case report illustrates the phenotypic variability of APECED with the absence of typical manifestations such as Addison's disease and hypoparathyroidism. APECED should thus be systematically suspected in young children presenting with cutaneous lesions associated with mucocutaneous candidiasis or auto-immune disease, even in the absence of known endocrinopathies. CONCLUSION: Dermatologists should be aware of this association since early diagnosis of APECED is critical in preventing life-threatening endocrinological crises.

Homozygous SMN1 exons 1-6 deletion: pitfalls in genetic counseling and general recommendations for spinal muscular atrophy molecular diagnosis.

We report on a rare homozygous intragenic deletion encompassing exons 1-6 of the SMN1 gene in a patient with spinal muscular atrophy (SMA) born into a consanguineous family. This exceptional configuration induced misinterpretation of the molecular defect involved in this patient, who was first reported as having a classic SMN1 exon 7 deletion. This case points out the possible pitfalls in molecular diagnosis of SMA in affected patients and their relatives: exploration of the SMN1 exon 7 (c.840C/T alleles) may be disturbed by several non-pathological or pathological variants around the SMN1 exon 7. In order to accurately describe the molecular defect in an SMA-affected patient, we propose to apply the Human Genome Variation Society nomenclature. This widely accepted nomenclature would improve the reporting of the molecular defect observed in SMA patients and thus would avoid the commonly used but imprecise terminology "absence of SMN1 exon 7."

Molecular characterization of MPS IIIA, MPS IIIB and MPS IIIC in Tunisian patients.

Sanfilippo syndrome (mucopolysaccharidosis type III, MPS III) is a progressive disorder in which patients are characterized by severe central nervous system degeneration together with mild somatic disease. MPS III results from a deficiency in one of the four enzymes involved in the heparan sulfate degradation, with sulfamidase (SGSH), α-N-acetylglucosaminidase (NAGLU), acetyl-coenzyme A: α-glucosaminide N-acetyltransferase (HGSNAT), and N-acetylglucosamine-6-sulfatase (GNS) being deficient respectively in MPS IIIA, MPS IIIB, MPS IIIC and MPS IIID. Mutation screening using PCR reaction/sequencing analysis on genomic DNA fragments was performed in seven Tunisian index cases with MPS IIIA, three with MPS IIIB and two with MPS IIIC. QMPSF (Quantitative Multiplex PCR of Short fluorescent Fragments) analysis was developed for the detection of genomic deletions and duplications in the SGSH gene. These approaches allowed the identification of 11 mutations, 8 of them were novel including a mutation involving the start codon (p.Met1?), one small duplication (p.Leu11AlafsX22), one small deletion (p.Val361SerfsX52) and a large deletion of exon 1 to exon 5 in the SGSH gene, one missense mutation (p.Pro604Leu) and one nonsense mutation (p.Tyr558X) in the NAGLU gene and, finally, one missense mutation (p.Trp627Cys) and one nonsense mutation (p.Trp403X) in the HGSNAT gene.

Clinical imaging and neuropathological correlations in an unusual case of cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive lipid storage disorder due to a deficiency of the mitochondrial enzyme sterol 27-hydroxylase (CYP 27) with reduced or no chenodeoxycholic synthesis. This deficiency leads to an accumulation of cholestanol in different sites such as the eye lens, central nervous system or tendons. We report a 64-year-old female patient with a progressive gait disorder associated with cognitive decline since the age of 59. The patient had no mental retardation, cataract or chronic diarrhea. Her family reported increasing behavioral modifications 10 years previously. Clinical examination revealed a spastic paraplegia and bilateral xanthomas on the Achilles tendons. Cerebral magnetic resonance imaging (MRI) revealed diffuse hyperintense T2 abnormalities in the pyramidal tracts from the internal capsules to the cerebral peduncles also Technetium-99m-ECD brain SPECT showed a severe cerebellar hypoperfusion. Serum cholestanol analysis was 7 µmol/l (N). After 2 years, she was bedridden and died of aspiration pneumonia. The neuropathological study confirmed the CTX diagnosis and the sequencing analysis revealed that she was compound heterozygous for two mutations in the CYP27A1 gene: 1435 C > T (exon 7) on one allele and a new mutation, 1017 G > C (exon 5) on the other. The interest of the present case is to report neuropathology findings strongly correlated with the MRI and SPECT abnormalities.

Autoimmune polyendocrine syndrome type 1 in north-western France: AIRE gene mutation specificities and severe forms needing immunosuppressive therapies.

BACKGROUND: Autoimmune polyendocrine syndrome type 1 (APS1) has been poorly evaluated in France. We focused on the north-western part of the country to describe clinical phenotypes, especially severe forms of the disease, and AIRE gene mutations. METHODS: Clinical and immunological data were collected, and pathological mutations were identified by DNA sequencing. RESULTS: Nineteen patients were identified with APS1. Clinical manifestations varied greatly, showing 1-10 components. Mucocutaneous candidiasis, adrenal failure, hypoparathyroidism, alopecia and other severe infections were the most frequent components. Four patients had severe forms, needing immunosuppressive therapy: 2 for hepatitis; 1 for severe malabsorption, and 1 for a T cell large granular lymphocytic leukemia. These therapies were very effective but caused general discomfort. One patient died of septicemia. Four different AIRE gene mutations were identified, and a 13-bp deletion in exon 8 (c.967-979del13) was the most prevalent. There was at least one allele correlating with this mutation and alopecia occurrence (p = 0.003). No novel mutation was detected. CONCLUSION: APS1 appears to be rare in north-western France. We identified 4 cases with a severe form needing immunosuppressive therapy. The AIRE gene mutations are more like those found in north-western Europe than those found in Finland.

[Genetics of mental retardation]. / Retards mentaux d'origine génétique.

Mental retardation affects nearly 3 % of the population. The causes of these disorders are various and are often not identified. Recent advances focused on the molecular basis of mental retardation. Nearly half of mental retardation syndromes have a genetic origin and the description of molecular, cytogenetic and metabolic alterations in these disorders led to the development of diagnostic tools. Indeed, identifying the precise origin of the mental retardation allows to improve patient care and to refine the prognosis. Moreover, these molecular tools will help the geneticist to evaluate the recurrence risk in the family in the genetic counseling step. On a fundamental point of view, the knowledge of molecular basis of mental retardation will help to understand the biological pathway which constitutes the first step before therapeutic strategies. Every patient with mental retardation should be investigated for causal origin of the disease. We will detail the diagnostic methods necessary to investigate a patient presenting with mental retardation. Then different examples of syndromes including a mental retardation will be chosen to illustrate different clinical situations.

MEF2C haploinsufficiency caused by either microdeletion of the 5q14.3 region or mutation is responsible for severe mental retardation with stereotypic movements, epilepsy and/or cerebral malformations.

BACKGROUND: Over the last few years, array-comparative genomic hybridisation (CGH) has considerably improved our ability to detect cryptic unbalanced rearrangements in patients with syndromic mental retardation. METHOD: Molecular karyotyping of six patients with syndromic mental retardation was carried out using whole-genome oligonucleotide array-CGH. RESULTS: 5q14.3 microdeletions ranging from 216 kb to 8.8 Mb were detected in five unrelated patients with the following phenotypic similarities: severe mental retardation with absent speech, hypotonia and stereotypic movements. Facial dysmorphic features, epilepsy and/or cerebral malformations were also present in most of these patients. The minimal common deleted region of these 5q14 microdeletions encompassed only MEF2C, the gene for a protein known to act in brain as a neurogenesis effector, which regulates excitatory synapse number. In a patient with a similar phenotype, an MEF2C nonsense mutation was subsequently identified. CONCLUSION: Taken together, these results strongly suggest that haploinsufficiency of MEF2C is responsible for severe mental retardation with stereotypic movements, seizures and/or cerebral malformations.

Clinical and molecular delineation of the 17q21.31 microdeletion syndrome.

BACKGROUND: The chromosome 17q21.31 microdeletion syndrome is a novel genomic disorder that has originally been identified using high resolution genome analyses in patients with unexplained mental retardation. AIM: We report the molecular and/or clinical characterisation of 22 individuals with the 17q21.31 microdeletion syndrome. RESULTS: We estimate the prevalence of the syndrome to be 1 in 16,000 and show that it is highly underdiagnosed. Extensive clinical examination reveals that developmental delay, hypotonia, facial dysmorphisms including a long face, a tubular or pear-shaped nose and a bulbous nasal tip, and a friendly/amiable behaviour are the most characteristic features. Other clinically important features include epilepsy, heart defects and kidney/urologic anomalies. Using high resolution oligonucleotide arrays we narrow the 17q21.31 critical region to a 424 kb genomic segment (chr17: 41046729-41470954, hg17) encompassing at least six genes, among which is the gene encoding microtubule associated protein tau (MAPT). Mutation screening of MAPT in 122 individuals with a phenotype suggestive of 17q21.31 deletion carriers, but who do not carry the recurrent deletion, failed to identify any disease associated variants. In five deletion carriers we identify a <500 bp rearrangement hotspot at the proximal breakpoint contained within an L2 LINE motif and show that in every case examined the parent originating the deletion carries a common 900 kb 17q21.31 inversion polymorphism, indicating that this inversion is a necessary factor for deletion to occur (p<10(-5)). CONCLUSION: Our data establish the 17q21.31 microdeletion syndrome as a clinically and molecularly well recognisable genomic disorder.

A cryopyrin-associated periodic syndrome with joint destruction.

OBJECTIVE: Describe four generations (11 members) of a family with a cryopyrin-associated periodic syndrome (CAPS), including joint destruction, associated with a CIAS1-gene mutation and good responses to anakinra. METHODS: In addition to detailed questioning and physical examination, six family members underwent haematological, immunological and biochemical testing. Exon 3 of the CIAS1 gene was sequenced in search of a mutation in the 1q44 region. RESULTS: During childhood or adolescence, four family members developed different combinations of the following CAPS manifestations: deafness (3/4); arthritis (4/4) with joint destruction for two of them; nervous (cerebral demyelinization, 2/4), cutaneous (livedo and/or urticaria, 3/4) and eye lesions (episcleritis and/or papilloedema, 4/4); IgA hypergammaglobulinaemia (4/4) and inflammatory syndrome (3/4). Sequencing of six family members' CIAS1-gene exon 3 identified a heterozygous mutation, c.1043C > T. Pertinently, this CAPS is distinct from chronic infantile neurological cutaneous and arthritis syndrome/neonatal onset multisystemic inflammatory disease syndrome and Muckle-Wells syndrome (MWS), which also result from exon 3 mutations in this gene. Moreover, this family did not have the usual neurological manifestations, typical morphological features and frequent amyloidosis of MWS. CONCLUSIONS: We describe a previously unreported form of CAPS with atypical neurological signs, joint destruction and livedo. This observation extends the clinical spectrum associated with CIAS1 mutations. Anakinra, an interleukin-1-receptor antagonist, prescribed to two family members, was highly effective.

Golli-MBP copy number analysis by FISH, QMPSF and MAPH in 195 patients with hypomyelinating leukodystrophies.

The inherited disorders of CNS myelin formation represent a heterogeneous group of leukodystrophies. The proteolipoprotein (PLP1) gene has been implicated in two X-linked forms, Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia type 2, and the gap junction protein alpha12 (GJA12) gene in a recessive form of PMD. The myelin basic protein (MBP) gene, which encodes the second most abundant CNS myelin protein after PLP1, presents rearrangements in hypomyelinating murine mutants and is always included in the minimal region deleted in 18q- patients with an abnormal hypomyelination pattern on cerebral MRI. In this study, we looked at the genomic copy number at the Golli-MBP locus in 195 patients with cerebral MRI suggesting a myelin defect, who do not have PLP1 mutation. Although preliminary results obtained by FISH suggested the duplication of Golli-MBP in 3 out of 10 patients, no abnormal gene quantification was found using Quantitative Multiplex PCR of Short Fluorescent fragments (QMPSF), Multiplex Amplifiable Probe Hybridization (MAPH), or another FISH protocol using directly-labelled probes. Pitfalls and interest in these different techniques to detect duplication events are emphasised. Finally, the study of this large cohort of patients suggests that Golli-MBP deletion or duplication is rarely involved in inherited defects of myelin formation.

Detection of genomic imbalances by array based comparative genomic hybridisation in fetuses with multiple malformations.

BACKGROUND: Malformations are a major cause of morbidity and mortality in full term infants and genomic imbalances are a significant component of their aetiology. However, the causes of defects in many patients with multiple congenital malformations remain unexplained despite thorough clinical examination and laboratory investigations. METHODS: We used a commercially available array based comparative genomic hybridisation method (array CGH), able to screen all subtelomeric regions, main microdeletion syndromes, and 201 other regions covering the genome, to detect submicroscopic chromosomal imbalances in 49 fetuses with three or more significant anomalies and normal karyotype. RESULTS: Array CGH identified eight genomic rearrangements (16.3%), all confirmed by quantitative multiplex PCR of short fluorescent fragments. Subtelomeric and interstitial deletions, submicroscopic duplications, and a complex genomic imbalance were identified. In four de novo cases (15qtel deletion, 16q23.1-q23.3 deletion, 22q11.2 deletion, and mosaicism for a rearranged chromosome 18), the genomic imbalance identified clearly underlay the pathological phenotype. In one case, the relationship between the genotype and phenotype was unclear, since a subtelomeric 6q deletion was detected in a mother and her two fetuses bearing multiple malformations. In three cases, a subtelomeric 10q duplication, probably a genomic polymorphism, was identified. CONCLUSIONS: The detection of 5/49 causative chromosomal imbalances (or 4/49 if the 6qtel deletion is not considered as causative) suggests wide genome screening when standard chromosome analysis is normal and confirms that array CGH will have a major impact on pre and postnatal diagnosis as well as providing information for more accurate genetic counselling.

Neurological presentation of a congenital disorder of glycosylation CDG-Ia: implications for diagnosis and genetic counseling.

The congenital disorders of glycosylation (CDG) constitute a new group of recessively inherited metabolic disorders that are characterized biochemically by defective glycosylation of proteins. Several types have been identified. CDG-Ia, the most frequent type, is a multisystemic disorder affecting the nervous system and numerous organs including liver, kidney, heart, adipose tissue, bone, and genitalia. A phosphomannomutase (PMM) deficiency has been identified in CDG-Ia patients and numerous mutations in the PMM2 gene have been identified in patients with a PMM deficiency. We report on a French family with 3 affected sibs, with an unusual presentation of CDG-Ia, remarkable for 1) the neurological presentation of the disease, and 2) the dissociation between intermediate PMM activity in fibroblasts and a decreased PMM activity in leukocytes. This report shows that the diagnosis of CDG-Ia must be considered in patients with non-regressive early-onset encephalopathy with cerebellar atrophy, and that intermediate values of PMM activity in fibroblasts do not exclude the diagnosis of CDG-Ia.

Identification of a novel mutation in the autoimmune regulator (AIRE-1) gene in a French family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is clinically characterized by the presence of two of the three major clinical symptoms: Addison's disease and/or hypoparathyroidism and/or chronic mucocutaneous candidiasis. Because of its autosomal recessive inheritance, this rare disorder constitutes an interesting model for understanding the molecular background of autoimmunity. Recently, mutations in the autoimmune regulator (AIRE-1) gene have been identified in APECED patients. Here we report, in a large French APECED family, the identification of a novel AIRE-1 missense mutation (Pro326Leu) in association with the Arg257Stop mutation which is detected in more than 80% of mutant Finnish AIRE-1 alleles. This Pro326Leu substitution occurs in the first plant homeodomain (PHD)-type zinc-finger domain of the protein which has been identified in a number of nuclear proteins involved in chromatin-mediated transcriptional regulation, such as ATRX, TIF1, KRIP-1 and Mi-2 autoantigen. This mutation highlights the key role of this amino acid in the structure of the PHD domain and confirms that exon 8 constitutes a mutational hotspot.

Prenatal diagnosis of hydrocephalus-stenosis of the aqueduct of Sylvius by ultrasound in the first trimester of pregnancy. Report of two cases.

Hydrocephalus-stenosis of the acqueduct of Sylvius sequence (HSAS) is characterized by hydrocephalus, macrocephaly, adducted thumbs, spasticity, agenesis of the corpus callosum and mental retardation. X-linked hydrocephalus is known to be due to mutations in the gene coding for the neural cell adhesion molecule L1 (L1-CAM) and diagnosis is made by identification of a mutation in the L1-CAM gene. Prenatal diagnosis of HSAS is usually suggested on ultrasound examination showing hydrocephalus in a male fetus associated with bilateral adducted thumbs. Mutation screening of the L1-CAM gene is indicated when neuropathological examination shows hypoplasia of the corticospinal tract associated with aqueductal stenosis. We report here two cases of HSAS diagnosed within the same family by ultrasound examination in the first trimester of pregnancy when bilateral adducted thumbs were the only early ultrasound marker.

Identification of novel L1CAM mutations using fluorescence-assisted mismatch analysis.

The L1CAM gene, which is located in Xq28 and codes for a neuronal cell adhesion molecule, is involved in three distinct conditions: HSAS (hydrocephalus-stenosis of the aqueduct of Sylvius), MASA (mental retardation, aphasia, shuffling gait, adductus thumbs), and SPG1 (spastic paraplegia). Molecular analysis of the L1CAM gene is labor-intensive because of the size of the coding region, which is fragmented in numerous exons, and because of the great allelic heterogeneity and distribution of the mutations. The FAMA (fluorescent assisted mismatch analysis) method combines the excellent sensitivity of the chemical cleavage method for scanning PCR fragments larger than 1 kb and the power of automated DNA sequencers. In order to optimize this method for L1CAM, we divided the gene into nine genomic fragments, each including three to four exons. These fragments were PCR-amplified using nine sets of primers containing additional rare universal sequences. A second-stage PCR, per formed with the two dye-labeled universal primers, allowed us to generate 1-kb-labeled fragments, which were then submitted to the chemical cleavage analysis. Among 12 French families with HSAS and/or MASA, we identified nine distinct L1CAM mutations, seven of which were novel, and an intronic variation. This study demonstrates that FAMA allows rapid and reliable detection of mutations in the L1CAM gene and thus represents one of the most appropriate methods to provide diagnosis for accurate genetic counseling in families with HSAS, MASA, or SPG1.