CACNA1A and spinocerebellar ataxia type 6: The allelic heterogeneity displayed by the CACNA1A gene also correlates with substantial clinical variation, as mutations in this gene are also responsible for two other autosomal dominant diseases: episodic ataxia type 2 (EA2, MIM #108500) and spinocerebellar ataxia type 6 (SCA6, MIM #183086).