Timothy syndrome (TS) is a severe multisystem disorder due to gain-of-function mutations in CACNA1C, encoding the pore-forming α-subunit of the ICa,L channel (CaV1.2), and results in bradycardia in almost all patients known, but caused by 2:1 atrioventricular block rather than sinus bradycardia (see footnote to Table S7). The gene discussed is CACNA1C; the disease is Timothy syndrome.