Cantù syndrome (CS, MIM # 239850) is a rare AD disorder caused by heterozygous gain-of-function variants in ABCC9 (97%, OMIM # 601439) and, rarely, in KCNJ8 (1–2%, OMIM # 600935), encoding the regulatory (SUR2) and pore-forming (Kir6.1) subunits, respectively, of ATP-sensitive potassium (KATP) channels [162]. The gene discussed is ABCC9; the disease is Cowden syndrome 1.