Phelan-McDermid syndrome is a rare genetic condition most commonly caused by a deletion (loss) of genetic material on chromosome 22. The specific region of chromosome 22 that is affected is called “22q13”, leading some to call it “22q13 deletion syndrome”. Phelan-McDermid syndrome may also be caused by a sequence (spelling) change (also called a disease-causing, or “pathogenic”, variant) in the SHANK3 gene.

This document outlines an overview of the genetics of Phelan-McDermid syndrome. Updated June 7, 2019