Molecular Diagnosis of Syndromic or Isolated Severe Intellectual Disability Using Whole Exome Sequencing : a Pilot Study

Inclusion Criteria: * Clinical diagnosis of syndromic or isolated severe intellectual disability (IQ \<50) without a molecular diagnosis * Recurrence in siblings (multiplex families) suggesting autosomal recessive inheritance (with or without parental consanguinity) or sporadic cases from a consanguineous union * Conventional genetic tests performed (including array-CGH) and MRI/CT-scan available * DNA samples from parents and from both unaffected or affected siblings available, for parental segregation and confirmation of candidate variations identified. * Availability of a signed informed consent * To be affiliated or beneficiary of French social security/healthcare system Exclusion Criteria: * Parents in the exclusion period of another study or as provided by the national register of volunteers * High-probability diagnostic hypothesis for which a molecular test is available at lower cost than exome sequencing