11th August 2024

Mitochondrial disorders

MERRF: Myoclonic epilepsy with ragged red fibres

The principal clinical features of MERRF are myoclonus, epilepsy, myopathy and ataxia, with neuropathy, visual problems, lipomas, spasticity, deafness and Wolff-Parkinson-White (WPW) syndrome. The characteristic ragged red fibres are found on muscle biopsy.

MELAS: Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes

Clinical features include stroke-like episodes, seizures, migraine-like headaches, deafness, short stature and myopathy.

MIDD: Maternally inherited diabetes and deafness

MIDD is characterised by insulin-dependent diabetes and sensorineural deafness, often alongside myopathy, visual problems, short stature, and cardiac and renal issues (focal segmental glomerulosclerosis).

MNGIE: Mitochondrial neurogastrointestinal encephalomyopathy

Clinical features include gastrointestinal dysmotility (secondary to visceral myopathy), ptosis, ophthalmoplegia, polyneuropathy and distal myopathy. Onset is from childhood to the 4th decade.

CPEO: Chronic progressive external ophthalmoplegia and KSS: Kearns-Sayre syndrome

Patients with CPEO develop ophthalmoplegia and ptosis. KSS has similar features with the addition of retinitis pigmentosa. Onset of KSS, generally in childhood, is earlier than that of CPEO (usually 4th decade).