Another, exceptionally rare, early-onset encephalopathic variant of hepatoencephalopathic mtDNA depletion is infantile onset spinocerebellar ataxia (IOSCA or MTDPS7, OMIM 271245), a disease due to a single, recessive mutation (p.Tyr508Cys) in the C10ORF2 gene, encoding the Twinkle helicase, which is part of the Finnish disease heritage [63]. Here, TWNK is linked to mitochondrial DNA depletion syndrome 7 (hepatocerebral type).