Mutations in C10orf2 cause dominantly inherited disorders, such as pure adult-onset PEO with multiple mtDNA deletions, or recessive clinical conditions including severe early-onset hepato-encephalopathy or infantile-onset spinocerebellar ataxia (IOSCA) and low mtDNA in the brain and liver, but not in skeletal muscle [6]. The gene discussed is TWNK; the disease is mitochondrial DNA depletion syndrome 7 (hepatocerebral type).