While the genetic causes of non-syndromic autism remain elusive, searches for a genetic cause have been successful to some extent in syndromic forms of autism. Syndromic autism is defined as autism in combination with additional clinical features. Co-morbidities often observed include intellectual disability, epilepsy, and psychiatric disorders. Frequent monogenic causes of syndromic autism include the fragile X syndrome and Rett syndrome [Amir et al., 1999; Rooms and Kooy, 2011]. Specific genomic disorders—submicroscopic chromosomal deletions or duplications at fixed positions in the genome—presenting with autism, include the duplication of the Prader–Willi/Angelman region at 15q11-13 and recurrent copy number variants (CNV) at 16p11.2 [Sanders et al., 2011]. A microscopically visible chromosomal abnormality associated with autism is an additional supernumerary isodicentric chromosome 15 [Mendelsohn and Schaefer, 2008]. Apart from recurrent genomic disorders, an excess of non-recurrent de novo CNVs as compared to healthy siblings and control subjects is also evident in patients with Autistic Spectrum Disorder (ASD) [Pinto et al., 2010].
