Table 1

Clinical phenotypes of POLG mutations

Inheritance	Name	Other names	Clinical features	Typical age at onset (years)
Autosomal recessive	Alpers–Huttenlocher syndrome		Liver dysfunction	0–10
			Occipital epilepsy
			Encephalopathy
	Syndrome of sensory ataxic neuropathy with ophthalmoparesis (SANDO)	Autosomal recessive progressive external ophthalmoplegia (arPEO)	Progressive external ophthalmoplegia	40–70
			Axonal sensorimotor neuropathy
			Myopathy
	Mitochondrial recessive ataxia syndrome (MIRAS)	Myoclonus, epilepsy, myopathy and sensory ataxia (MEMSA)	Occipital epilepsy	0–30
			Myoclonus
			Ataxia
		Ataxia neuropathy spectrum syndrome (ANS)	Ataxia
		Ataxia neuropathy spectrum syndrome (ANS)	Axonal sensorimotor neuropathy
		Myocerebrohepatopathy syndrome (MCHS)	Encephalopathy
			Myopathy
			Liver dysfunction
Autosomal dominant	Autosomal dominant progressive external ophthalmoplegia (adPEO)		Progressive external ophthalmoplegia	40–70
			Parkinsonism
			Premature ovarian failure