PTEN and Cowden syndrome 1: The phosphatase and tensin homolog hamartoma tumor syndrome (PHTS) refers to a spectrum of disorders caused by variants of the phosphatase and tensin homolog (PTEN) gene, including Cowden syndrome (CS), Bannayan–Riley–Ruvalcaba syndrome, adult Lhermitte–Duclos disease (LDD), and autism spectrum disorders associated with macrocephaly.