Clinical Research Directory

1. Inclusion criteria for children or adults with ID of unknown etiology (index case) In order to be eligible to participate in this study, an individual must meet all the following criteria: * Age: 1. Between 0 and 5 years with stringent criteria (severe delayed development in terms of motor skills, language, and/or sociability) OR 2. ≥ 6 years: patients with ID, whatever the severity (but with proven ID by ad hoc neuropsychological testing) and the associated manifestations * Without any obvious diagnosis identified during a genetic consultation in one of the participating center (i.e., an obvious syndrome with ID with well-known molecular diagnosis is excluded); * Provision of signed and dated of "participant" consent form; * Stated willingness to comply with all study procedures and availability for the duration of the study. Patient with a social security in compliance with the French law (Provisions relating to research involving the human person provided for in Articles L 1121-1 et seq. of the French Public Health Code). 2. Inclusion criteria for biological parents \- Provision of signed and dated of both parents consent form. 3. Non-inclusion criteria * An individual, who presents any condition which in the investigator's opinion makes it undesirable for the subject to participate in the trial or which would jeopardize compliance with the protocol, will not be eligible; * Patients with isolated learning disabilities; * One or both parents with ID; * Parent placed under judicial protection (tutelle, curatelle et sauvegarde de justice) ; * Patient with a known etiological diagnosis (non-genetic, previously proven Fra-X syndrome, know chromosomal anomaly, known pathogenic or probably pathogenic variant identified in an ID gene by any technique). * For patient concerning by biobank project: hypersensitivity to local anesthesia