In fact, TWNK mutations also cause mtDNA depletion, associated with more severe phenotypes, such as infantile onset spinocerebellar ataxia (IOSCA) [59], or other phenotypic variants associated with mtDNA multiple deletions such as Perrault syndrome [60,61]. Here, TWNK is linked to mitochondrial DNA depletion syndrome 7 (hepatocerebral type).