Probands with a documented history of clinical diagnosis of ASD were recruited at Children’s Hospital Boston. To participate, they had to be over 24 months of age and have at least one biological parent or an affected sibling available. Subjects were excluded if they had an underlying metabolic disorder or any chronic systemic disease, an acquired developmental disability (e.g. birth asphyxia, trauma-related injury, meningitis, etc.), or cerebral palsy. All participants provided informed consent and a phenotyping battery was performed including the Autism Diagnostic Observation Schedule (ADOS), the Autism Diagnostic Interview- Revised (ADI-R) and other measures to assess cognitive status. 75% of subjects with a clinical diagnosis met strict research criteria for ASD on both ADI-R and ADOS. In addition, a complete family and medical history was obtained.
