Disease Directory MERRF Syndrome
Mitochondrial

MERRF Syndrome

Also known as: myoclonic epilepsy with ragged red fibres, MT-TK mutation

Prevalence

Rare; estimated fewer than 1 in 400,000

Onset

Childhood to early adulthood

Type

Rare mitochondrial disease

Gene

MT-TK (mtDNA)

About MERRF Syndrome

MERRF syndrome is a maternally inherited mitochondrial disorder characterised by myoclonic epilepsy, cerebellar ataxia, myopathy with ragged red fibres on muscle biopsy, and progressive neurological deterioration. The most common causative mutation is m.8344A>G in MT-TK, which encodes mitochondrial tRNA-Lys and disrupts oxidative phosphorylation. The clinical spectrum is broad, ranging from mild myoclonus to severe multisystem disease, influenced by mutation heteroplasmy levels across tissues.

Common Clinical Features

Myoclonus (stimulus-sensitive jerking) Generalised seizures Cerebellar ataxia Myopathy with ragged red fibres Sensorineural hearing loss Dementia or cognitive decline Short stature and exercise intolerance

Clinical Trial Eligibility Tips

What to know before applying to MERRF Syndrome trials.

Muscle biopsy showing ragged red fibres and/or confirmed MT-TK mutation is the primary diagnostic requirement for most MERRF studies; ensure pathology reports are available.

Heteroplasmy levels in muscle tissue are more informative than blood for this disorder; request tissue-specific genetic testing if blood results are inconclusive.

Anti-epileptic drug regimens may interact with investigational agents; provide a complete medication list including valproate, which is often contraindicated in mitochondrial disease.

Patient Resources

Patient Organization

United Mitochondrial Disease Foundation

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Natural History Registry

North American Mitochondrial Disease Consortium (NAMDC) Registry

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Orphanet

European reference resource for rare diseases (ORPHA:551)

View on Orphanet ↗

NORD

National Organization for Rare Disorders

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Find recruiting MERRF Syndrome trials

Search 500,000+ studies from ClinicalTrials.gov, filtered for MERRF Syndrome. Updated daily.

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