SHANK3 and atypical Rett syndrome: SHANK3 maps in the subtelomeric region of chromosome 22q (22q13.33), encodes a multidomain scaffold protein of the post-synaptic density of several types of excitatory synapses, and its pathogenic alterations have been associated with several disorders, including, in addition to PMS-SHANK3 related [5,6,8], autism spectrum disorder (ASD), schizophrenia, a Rett syndrome-like phenotype, and intellectual disability [27].