ABCC9 and Cowden syndrome 1: Importantly, as the number of genetically confirmed CS cases has risen, it has become clear that residue R1154 in SUR2 is particularly susceptible to mutation, with 24 of 72 patients (20 of 57 unrelated families) carrying variants ABCC9[c.3461G>A], ABCC9[c.3460C>T], or ABCC9[c.3460C>G], which encode SUR2[p.R1154Q], SUR2[p.R1154W], and SUR2[p.R1154G], respectively (24).