Mitochondrial DNA depletion syndrome-7 is an autosomal recessive severe neurodegenerative disorder characterized primarily by hypotonia, ataxia, ophthalmoplegia, hearing loss, seizures, and sensory axonal neuropathy. Although originally classified as a form of spinocerebellar ataxia , it has been reclassified as a mitochondrial DNA depletion syndrome based on the finding of mtDNA depletion in the brain and liver of affected individuals. [From OMIM]