Two hereditary cation-leaky conditions, overhydrated stomatocytosis (OHSt) and stomatin-deficient cryohydrocytosis (sdCHC), are caused by mutations in non-band 3 erythrocyte membrane proteins and produce large amounts of misfolded protein but have not been associated with dyserythropoiesis (Bruce et al., 2009; Flatt et al., 2011; Bawazir et al., 2012). Here, STOM is linked to overhydrated hereditary stomatocytosis.