The mutation in the gene for puratrophin, known as the PLEKHG4 gene (Chromosome 16q22) isassociated with the pure cerebellar ataxia form of Japanese SCA 4 (which isclassically characterized as sensory axonal neuropathy), and now also withJapanese dominant ataxia caused by the PLEKHG4 mutation, which has beenreassigned as SCA R4. The gene discussed is PLEKHG4; the disease is Sensory axonal neuropathy.