Gain-of-function (GoF) mutations in the muscle-type Kir6.1 and SUR2 subunits of KATP channels are associated with an autosomal dominant disorder, Cantú Syndrome (CS).5,6 Over 30 mutations in KCNJ8 and ABCC9 have now been linked to CS.6–8. Here, ABCC9 is linked to Cowden syndrome 1.