The phenotypic spectrum of POLG-related mitochondrial disease includes progressive external ophthalmoplegia (PEO), sensory and cerebellar ataxia, encephalopathy, neuropathy, focal and generalised epilepsy, dysarthria, distal myopathy, Parkinsonism, liver disease and premature ovarian failure [2–10]. The gene discussed is POLG; the disease is inborn mitochondrial metabolism disorder.