We observed that one patient with LQT9 also had prominent U-waves (Vatta et al., 2006), which is an electrocardiographic feature seen in patients with loss of function mutations in the Kir2.1 related to Andersen-Tawil Syndrome (ATS1) (Tristani-Firouzi et al., 2002). The gene discussed is KCNJ2; the disease is Cardiodysrhythmic potassium-sensitive periodic paralysis.