KCNH2 and deafness: Congenital forms are caused by mutations in one of 16 different genes (Schwartz et al, 2013), most patients presenting with mutations in KCNQ1 [defined as LQT1 when heterozygous and Jervell and Lange‐Nielsen syndrome (JLNS) when homozygous and associated with deafness (Jervell & Lange‐Nielsen, 1957)], KCNH2 (LQT2) or SCN5A (LQT3) genes (Schwartz et al, 2001).