Mitochondrial myopathies

- mitochondrial diseases are maternally inherited

Chronic progressive external ophthalmoplegia (CPEO)
- slowly progressive paralysis of extraocular muscles
- bilateral, symmetrical, progressive ptosis followed by ophthalmoparesis months to years later

Leber's hereditary optic neuropathy (LHON)
- characterised by blindness, ataxia, peipheral neuropathy and cardiac arrhythmias
- usually affects men, most commonly in the late twenties or early thirties
- commonest cause of blindness in young men

MELAS (myopathy, encephalopathy, lactic acidosis and stroke like episodes)
- lactic acidosis: high lactate to pyruvate ratio
- proximal myopathy, hypotonia, seizure and sttoke like episodes

MERRF (myoclonic epilepsy, ragged red fibres)
- myoclonic seizure that are usually sudden, brief, jerking spasm that can affect the limbs or the entire body
- short stature, deafness, ataxia, dysarthria, optic atrophy, dementia and nystagmus can occur

Kearns-Sayre syndrome
- ophthalmoplegia, heart block, cerebellar ataxia, deafness and mental deficiency

Pearson syndrome
- lactic acidosis, pancreatic insufficiency and pancytopenia