To date, most patients with PMS have been diagnosed by microarray identifying a telomeric 22q deletion of variable size (from a dozen kb to few Mb). Few patients have been identified using FISH technology or conventional karyotyping.

PMS are mostly associated with pure 22qdeletion but few patients have unbalanced translocation that either occurred de novo or resulted from derivative parental balanced translocation. For genetic testing, patients carrying SHANK3 point mutations may be under-detected due to the very GC rich regions of some exons. This leads to a low coverage by whole exome sequencing (WES). Genetic testing should favor PCR-free whole genome sequencing (WGS). Primers for Sanger sequencing can be found here.

For treatment, there is no specific approach. A European clinical guideline for patients with PMS will be soon available. Lithium has been proposed to increase SHANK3 expression and to reduce the symptoms in mouse models of SHANK3 and in patients. A clinical trial is in progress to test the efficacy of lithium in patients with SHANK3 mutations.