ITPR1 and cerebellar ataxia: Prior to the identification of ITPR1 mutations causing GS, two aniridia cases with GS features were reported with PAX6 mutations: one had a non-coding exon essential-splice mutation and no ataxia or cerebellar abnormalities (Ticho et al. 2006), and the second, with a typical PAX6 stop-gain mutation, had ataxia but no cerebellar abnormalities (Graziano et al. 2007).