The clinical phenotypes associated with POLγ impairment are highly heterogeneous and include Alpers-Huttenlocher encephalopathy (AHS), ataxia syndromes such as mitochondrial recessive ataxia syndrome (MIRAS) and sensory ataxia neuropathy, dysarthria, and ophthalmoplegia (SANDO), and autosomal dominant or autosomal recessive progressive external ophthalmoplegia (PEO)6. Here, POLG is linked to recessive mitochondrial ataxia syndrome.