Phelan-McDermid syndrome (PHMDS) or 22q13.3 deletion syndrome (OMIM 606232) is a rare, genetic disorder caused by a haploinsufficiency of the SHANK3 gene resulting from either a point mutation or an heterozygous deletion on the distal long arm of chromosome 22 (Kolevzon et al. Here, SHANK3 is linked to Phelan-McDermid syndrome.