ATP8A2 and cerebellar ataxia: Similarly, the only reported patient with the OMIM phenotype of cerebellar ataxia, mental retardation, and dysequilibrium syndrome had a single missense variant in ATP8A2 whereas the patient we present with a homozygous truncating variant has physical and cognitive delay, failure to thrive, vision impairment, hypotonia, eczema and leukodystrophy.