Germline mutations involving the PTEN gene have been associated with a spectrum of related genetic disorders collectively referred to as PTEN hamartoma tumor syndromes (PHTS), which include Cowden syndrome (CS), Bannayan–Riley–Ruvalcaba syndrome (BRRS), adult Lhermitte–Duclos disease, and autism spectrum disorders associated with macrocephaly [44]. The gene discussed is PTEN; the disease is Cowden syndrome 1.