NRXN1 and Phelan-McDermid syndrome: Hence, the present study was designed to compare two synaptic gene conditions with high penetrance for autism; Phelan-McDermid Syndrome (PMS, also known as 22q13 deletion syndrome, typically including haploinsufficiency of the SHANK3 gene) and NRXN1 deletions (NRXN1ds).