Autism with dell5p.11.1: case report with a new cytogenetic finding: Autism is a neurodevelopmental disorder and believed to be mainly genetic in origin, and environmental factors may modulate phenotypic expression. Less than four percent of cases of autism are associated with chromosomal abnormalities. Cytogenetic abnormalities found at the 15q11-q13 locus are reported most frequently in patients with autism. We performed GTG-banding and FISH studies to the present case and his parents and found a maternally inherited deletion on chromosome 15p in this case. With an understanding of the many genetic causes of autism, prenatal screening and counseling may one day become available for affected families as more autism-causing conditions become diagnosable.