KCNH1 and Zimmermann-Laband syndrome: We studied a total of 36 individuals with a variant likely affecting function in a potassium channel encoding gene, including eight newly reported individuals, and determined the frequency of overlapping clinical features typical for TBS, ZLS, and FHEIG syndromes in the 27 individuals with dominant KCNH1 variants, six with dominant KCNN3, and three with dominant KCNK4 variants.