KCNJ8 and Cowden syndrome 1: CS is caused by gain‐of‐function (GoF) pathogenic variants in ABCC9 and, less commonly, in KCNJ8, which encode the regulatory (SUR2) and pore‐forming (Kir6.1) subunits, respectively, of ATP‐sensitive potassium (KATP) channels(Brownstein et al., 2013; Cooper et al., 2014; Harakalova et al., 2012; McClenaghan et al., 2017; van Bon et al., 2012).