Phelan-McDermid Syndrome [PMS; under the Autism Spectrum Disorders (ASD) umbrella] is a rare genetic condition caused by deletion or de novo pathological variation of the long arm terminal end of chromosome 22 (location q13.3; also referred to as 22q13.3 deletion syndrome) within the Shank3 gene [47]. Here, SHANK3 is linked to Monosomy 22q13.