Search

Polymicrogyria (PMG) is a heterogeneous brain malformation that may result from prenatal vascular disruption or infection, or from numerous genetic causes that still remain difficult to identify. We identified three unrelated patients with polymicrogyria and duplications of chromosome 2p, defined the smallest region of overlap, and performed gene pathway analysis using Cytoscape. The smallest region of overlap in all three children involved 2p16.1-p16.3. All three children have bilateral perisylvian polymicrogyria (BPP), intrauterine and postnatal growth deficiency, similar dysmorphic features, and poor feeding. Two of the three children had documented intellectual disability. Gene pathway analysis suggested a number of developmentally relevant genes and gene clusters that were over-represented in the critical region. We narrowed a rare locus for polymicrogyria to a region of 2p16.1-p16.3 that contains 33-34 genes, 23 of which are expressed in cerebral cortex during human fetal development. Using pathway analysis, we showed that several of the duplicated genes contribute to neurodevelopmental pathways including morphogen, cytokine, hormonal and growth factor signaling, regulation of cell cycle progression, cell morphogenesis, axonal guidance, and neuronal migration. These findings strengthen the evidence for a novel locus associated with polymicrogyria on 2p16.1-p16.3, and comprise the first step in defining the underlying genetic etiology.

BACKGROUND: Undetected ear and hearing problems negatively impact the quality of life of people with intellectual disability. METHODS: This multicentre retrospective study describes the outcome of 10 years of ear and hearing screening in athletes with intellectual disability in seven European countries. The screening was conducted by a trained team using a strictly standardised protocol. RESULTS: Of 15,363 screened athletes with intellectual disability, more than half (58.7%) needed referral for ear and/or hearing problems, ranging from 51.7% (

PURPOSE: This study investigated whole-exome sequencing (WES) yield in a subset of intellectually disabled patients referred to our clinical diagnostic center and calculated the total costs of these patients' diagnostic trajectory in order to evaluate early WES implementation.METHODS: We compared 17 patients' trio-WES yield with the retrospective costs of diagnostic procedures by comprehensively examining patient records and collecting resource use information for each patient, beginning with patient admittance and concluding with WES initiation. We calculated cost savings using scenario analyses to evaluate the costs replaced by WES when used as a first diagnostic tool.RESULTS: WES resulted in diagnostically useful outcomes in 29.4% of patients. The entire traditional diagnostic trajectory average cost was $16,409 per patient, substantially higher than the $3,972 trio-WES cost. WES resulted in average cost savings of $3,547 for genetic and metabolic investigations in diagnosed patients and $1,727 for genetic investigations in undiagnosed patients.CONCLUSION: The increased causal variant detection yield by WES and the relatively high costs of the entire traditional diagnostic trajectory suggest that early implementation of WES is a relevant and cost-efficient option in patient diagnostics. This information is crucial for centers considering implementation of WES and serves as input for future value-based research into diagnostics.Genet Med 18 9, 949-956.

Intellectual disability (ID) is a very heterogeneous disorder with over 100 ID genes located on the X chromosome alone. Of these, KDM5C and IQSEC2 are located adjacent to each other at the Xp11.22 locus. While mutations in either of these genes are associated with severe ID in males, female carriers are mostly unaffected. Here, we report on a female patient with severe ID and autistic features carrying a de novo 0.4 Mb deletion containing six coding genes including KDM5C and IQSEC2. X-inactivation analysis revealed skewing in a lymphocyte-derived cell line from this patient with preferential inactivation of the mutant X chromosome. As the brain-expressed KDM5C and IQSEC2 genes escape X-inactivation, deletion of these alleles could still be detrimental despite skewing of X-inactivation. Indeed, mutations in either of both genes have been reported in a few female ID patients. Expression analysis in the patients' cell line revealed decreased KDM5C mRNA levels compared to female controls. IQSEC2 levels could not be compared due to very low expression in blood. Overall, our data suggest that heterozygous loss-of-function of the escape genes KDM5C and/or IQSEC2 can contribute to severe ID in female patients and should be taken into account in diagnostics.

PurposeMowat-Wilson syndrome (MWS) is a rare intellectual disability/multiple congenital anomalies syndrome caused by heterozygous mutation of the ZEB2 gene. It is generally underestimated because its rarity and phenotypic variability sometimes make it difficult to recognize. Here, we aimed to better delineate the phenotype, natural history, and genotype-phenotype correlations of MWS.MethodsIn a collaborative study, we analyzed clinical data for 87 patients with molecularly confirmed diagnosis. We described the prevalence of all clinical aspects, including attainment of neurodevelopmental milestones, and compared the data with the various types of underlying ZEB2 pathogenic variations.ResultsAll anthropometric, somatic, and behavioral features reported here outline a variable but highly consistent phenotype. By presenting the most comprehensive evaluation of MWS to date, we define its clinical evolution occurring with age and derive suggestions for patient management. Furthermore, we observe that its severity correlates with the kind of ZEB2 variation involved, ranging from ZEB2 locus deletions, associated with severe phenotypes, to rare nonmissense intragenic mutations predicted to preserve some ZEB2 protein functionality, accompanying milder clinical presentations.ConclusionKnowledge of the phenotypic spectrum of MWS and its correlation with the genotype will improve its detection rate and the prediction of its features, thus improving patient care.GENETICS in MEDICINE advance online publication, 4 January 2018; doi:10.1038/gim.2017.221. ispartof: Genetics in Medicine vol:20 issue:9 pages:965-975 ispartof: location:United States status: published

The evaluation of facial dysmorphism is a critical step toward reaching a diagnostic. The aim of the present study was to evaluate the ability to interpret facial morphology in African children with intellectual disability (ID). First, 10 experienced clinicians (5 from Africa and 5 from Europe) rated gestalt in 127 African non-Down Syndrome (non-DS) patients using either the score 2 for "clearly dysmorphic", 0 for "clearly non dysmorphic" or 1 for "uncertain". The inter-rater agreement was determined using kappa coefficient. There was only fair agreement between African and European raters (kappa-coefficient = 0.29). Second, we applied the FDNA Face2Gene solution to assess Down Syndrome (DS) faces. Initially, Face2Gene showed a better recognition rate for DS in Caucasian (80 %) compared to African (36.8 %). We trained the Face2Gene with a set of African DS and non-DS photographs. Interestingly, the recognition in African increased to 94.7 %. Thus, training improved the sensitivity of Face2Gene. Our data suggest that human based evaluation is influenced by ethnic background of the evaluator. In addition, computer based evaluation indicates that the ethnic of the patient also influences the evaluation and that training may increase the detection specificity for a particular ethnic. ispartof: Clinical Genetics vol:92 issue:2 pages:166-171 ispartof: location:Denmark status: published

The advent of next-generation sequencing has proven to be a key force in the identification of new genes associated with intellectual disability. In this study, high-throughput sequencing of the coding regions of the X-chromosome led to the identification of a missense variant in the HUWE1 gene. The same variant has been reported before by Froyen et al. (2008). We compare the phenotypes and demonstrate that, in the present family, the HUWE1 mutation segregates with the more severe ID phenotypes of two out of three brothers. The third brother has a milder form of ID and does not carry the mutation.

International audience; KAT6B sequence variants have been identified previously in both patients with the Say-Barber-Biesecker type of blepharophimosis mental retardation syndromes (SBBS) and in the more severe genitopatellar syndrome (GPS). We report on the findings in a previously unreported group of 57 individuals with suggestive features of SBBS or GPS. Likely causative variants have been identified in 34/57 patients and were commonly located in the terminal exons of KAT6B. Of those where parental samples could be tested, all occurred de novo. Thirty out of thirty-four had truncating variants, one had a missense variant and the remaining three had the same synonymous change predicted to affect splicing. Variants in GPS tended to occur more proximally to those in SBBS patients, and genotype/phenotype analysis demonstrated significant clinical overlap between SBBS and GPS. The de novo synonymous change seen in three patients with features of SBBS occurred more proximally in exon 16. Statistical analysis of clinical features demonstrated that KAT6B variant-positive patients were more likely to display hypotonia, feeding difficulties, long thumbs/great toes and dental, thyroid and patella abnormalities than KAT6B variant-negative patients. The few reported patients with KAT6B haploinsufficiency had a much milder phenotype, though with some features overlapping those of SBBS. We report the findings in a previously unreported patient with a deletion of the KAT6B gene to further delineate the haploinsufficiency phenotype. The molecular mechanisms giving rise to the SBBS and GPS phenotypes are discussed.

Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability, developmental delay, lack of speech, and epileptic seizures. Previous studies have indicated that children with AS due to 15q11.2-q13 deletions have a more severe developmental delay and present more often autistic features than those with AS caused by other genetic etiologies. The present study investigated the neurodevelopmental profiles of the different genetic etiologies of AS, and examined the evolution of mental development and autistic features over a 12-year period in children with a 15q11.2-q13 deletion. This study included 42 children with AS. Twelve had a Class I deletion, 18 had Class II deletions, three showed atypical large deletions, five had paternal uniparental disomy (pUPD) and four had UBE3A mutations. Children with a deletion (Class I and Class II) showed significantly reduced developmental age in terms of visual perception, receptive language, and expressive language when compared to those with a UBE3A mutation and pUPD. Within all subgroups, expressive language performance was significantly reduced when compared to the receptive performance. A follow-up study of seven AS cases with 15q11.2-q13 deletions revealed that over 12 years, the level of autistic features did not change, but both receptive and expressive language skills improved. (C) 2014 Elsevier Ltd. All rights reserved. Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability, developmental delay, lack of speech, and epileptic seizures. Previous studies have indicated that children with AS due to 15q11.2-q13 deletions have a more severe developmental delay and present more often autistic features than those with AS caused by other genetic etiologies. The present study investigated the neurodevelopmental profiles of the different genetic etiologies of AS, and examined the evolution of mental development and autistic features over a 12-year period in children with a 15q11.2-q13 deletion. This study included 42 children with AS. Twelve had a Class I deletion, 18 had Class II deletions, three showed atypical large deletions, five had paternal uniparental disomy (pUPD) and four had UBE3A mutations. Children with a deletion (Class I and Class II) showed significantly reduced developmental age in terms of visual perception, receptive language, and expressive language when compared to those with a UBE3A mutation and pUPD. Within all subgroups, expressive language performance was significantly reduced when compared to the receptive performance. A follow-up study of seven AS cases with 15q11.2-q13 deletions revealed that over 12 years, the level of autistic features did not change, but both receptive and expressive language skills improved.

Genome-wide array comparative genome hybridization has become the first in line diagnostic tool in the clinical work-up of patients presenting with intellectual disability. As a result, chromosome X-copy number variations are frequently being detected in routine diagnostics. We retrospectively reviewed genome wide array-CGH data in order to determine the frequency and nature of chromosome X-copy number variations (X-CNV) in a cohort of 2222 sporadic male patients with intellectual disability (ID) referred to us for diagnosis. In this cohort, 68 males were found to have at least one X-CNV (3.1%). However, correct interpretation of causality remains a challenging task, and is essential for proper counseling, especially when the CNV is inherited. On the basis of these data, earlier experience and literature data we designed and propose an algorithm that can be used to evaluate the clinical relevance of X-CNVs detected in sporadic male ID patients. Applied to our cohort, 19 male ID patients (0.85%) were found to carry a (likely) pathogenic X-CNV.

We report two cases of a peculiar leukoencephalopathy with temporal cysts. Both patients have a non-progressive neurological disorder with mental retardation, microcephaly and sensorineural deafness although clinical differences between them may reflect a different aetiology. The metabolic disorders with white matter involvement and the recently described leukoencephalopathies (Van Der Knaap disease, 'vanishing white matter disease') were excluded based on clinical, biologic and imaging findings. Cytomegalovirus infection is a likely possibility in the first case although the magnetic resonance imaging picture is only partially similar to previously reported cases. Our patients are strikingly similar to the patients reported by Deonna et al. and Olivier et al. We discuss the clinical and imaging findings in our patients and the differential diagnosis considering the known disorders of the white matter in childhood.

The Pallister-Killian syndrome is a rare disorder, which is clinically diagnosed and usually confirmed by the detection of mosaicism for an isochromosome 12p in fibroblast cultures. To date FISH on buccal mucosa has been used in only three cases and this detected high levels of mosaicism for the isochromosome. We review one previously reported case [Woodman et al. (1995) Genet Couns 6:33-36] and report a further seven clinically suspected cases in which the diagnoses were confirmed by FISH on buccal mucosa, and recommend that this tissue be used routinely for laboratory confirmation. The presence of the isochromosome 12p at levels as low as 1% is acceptable.