Apart from PEO, mutations in the TWNK gene have been discovered in a variety of mitochondrial illnesses, including mtDNA depletion syndromes (MDSs), Perrault syndrome, infantile-onset spinocerebellar ataxia (IOSCA), and other ataxia neuropathies (Hudson et al., 2005; Hakonen et al., 2008; Lonnqvist et al., 2009; Van Hove et al., 2009; Fratter et al., 2010). Here, TWNK is linked to mitochondrial DNA depletion syndrome 7 (hepatocerebral type).