MERRF (myoclonic epilepsy with ragged red fibers)
Log in to starLast updated 2mo ago
Log in to add personal notes on this page.
A patient with myoclonic seizures, ataxia, and myopathy has multiple lipomas. Muscle biopsy shows ragged red fibers.
Maternal (mtDNA); MT-TK m.8344A>G (~80%)
- Myoclonic epilepsy
- Ataxia
- Myopathy with ragged red fibers
- Multiple lipomas
- Short stature
- Muscle biopsy: ragged red fibers (modified Gomori trichrome), COX-deficient fibers
- Elevated serum/CSF lactate (and lactate-to-pyruvate ratio)
- Confirmation: mtDNA testing for MT-TK m.8344A>G (most informative in muscle given heteroplasmy)
- Largely supportive (no disease-modifying therapy); anticonvulsants for myoclonus and seizures (avoid valproate, which can worsen mitochondrial function)
- "Mitochondrial cocktail" (CoQ10, L-carnitine, riboflavin) is commonly used though evidence is limited
- Maternally inherited (mtDNA): all offspring of an affected mother are at risk; recurrence risk is not predictable from heteroplasmy
MERFF, Round, Fatty lipomas: the "RF" in MERRF reminds you of the Round, Fatty lipomas that are distinctive to this disorder.
Myoclonus is the first symptom: the "M" in MERRF stands for Myoclonic epilepsy, which is typically the initial presentation. Ragged Red Fibers on muscle biopsy complete the name.