SHANK3 haploinsuffiency on account of the heterozygous loss of the distal arm of chromosome 22 or to mutations within the SHANK3 gene [5] leads to a syndromic form of a neurodevelopmental autism spectrum disorder (ASD) named 22q13.3 deletion or Phelan-McDermid Syndrome (PMDS) [6–8]. The gene discussed is SHANK3; the disease is Monosomy 22q13.