Abstract
Autism spectrum disorders (ASDs) are highly heritable. Gene discovery promises to help illuminate the pathophysiology of these syndromes, yielding opportunities for the development of novel treatments and understanding of their natural history. Although the underlying genetic architecture of ASDs is not yet known, the literature demonstrates that it is not a monogenic disorder with mendelian inheritance, rather a group of complex genetic syndromes with risk deriving from genetic variations in multiple genes. This article reviews the origins of the common versus rare variant debate, highlights recent findings in the field, and addresses the clinical implications of common and rare variant discoveries.