CACNA1A and pathologic nystagmus: In addition to ID/GDD, most cases with CACNA1A variants present with ataxia, epilepsy, attention deficit hyperactive disorder, autism spectrum disorder, dysmorphic features and eye abnormalities such as nystagmus, paroxysmal tonic upgaze, dysmetric saccades, blindness, myoclonus, ocular apraxia, exophthalmos and bilateral esotropia.