CACNA1C and familial long QT syndrome: Pathogenic variants in the L‐type Ca2+ channel gene CACNA1C (OMIM 114205) were first identified in a series of patients manifesting a multi‐system disorder that included severe long QT syndrome (LQTS), congenital heart disease, dysmorphic facial features, syndactyly, abnormal immune function, and neuropsychiatric disorders, collectively known as Timothy syndrome (OMIM 601005) (Splawski et al., 1993).