ATP8A2 and cerebellar ataxia, intellectual disability, and dysequilibrium: ATP8A2, another P4-ATPase highly expressed in the brain, has been implicated in a recessive disorder characterized by cerebellar ataxia, ID, and disequilibrium syndrome (CAMRQ, MIM 615268), or severe hypotonia, ID, and optic atrophy with or without encephalopathy32–36.