POLG and recessive mitochondrial ataxia syndrome: These include, in particular, POLG-related diseases (i.e., ataxia-myopathy syndrome; “mitochondrial recessive ataxia syndrome,” or MIRAS; ataxia with ocular myopathy and, more rarely, with psychiatric comorbidities or epilepsy) and certain C10orf2 (“Twinkle”) mutations, which can cause infantile-onset spinocerebellar ataxia (IOSCA), a severe neurodegenerative disorder characterized by progressive atrophy of the brainstem, cerebellum, and spinal cord, and by sensory axonal neuropathy.