MERRF

MERRF syndrome (Myoclonic Epilepsy with Ragged-Red Fibers) is a rare mitochondrial disorder that primarily affects the nervous system and skeletal muscles. Also known as Fukuhara syndrome, MERRF is caused by mutations in mitochondrial DNA (mtDNA), most commonly the m.8344A>G mutation in the MT-TK gene encoding tRNA-Lysine. Because mitochondria are responsible for producing cellular energy, tissues with high energy demands — particularly the brain, muscles, and nerves — are most severely affected. The hallmark features of MERRF include myoclonus (sudden, brief involuntary muscle jerks), generalized epilepsy, cerebellar ataxia (impaired coordination and balance), and myopathy with characteristic ragged-red fibers seen on muscle biopsy. Additional features may include short stature, hearing loss (sensorineural deafness), optic atrophy, cardiomyopathy, peripheral neuropathy, dementia or cognitive decline, and lipomas (particularly in the neck and trunk region). The severity and combination of symptoms can vary considerably, even among members of the same family, due to heteroplasmy — the variable proportion of mutant versus normal mitochondrial DNA in different tissues. There is currently no cure for MERRF syndrome. Treatment is supportive and symptomatic, focusing on seizure management with antiepileptic drugs (though sodium valproate should be used with caution in mitochondrial disorders), physical therapy for ataxia and myopathy, and management of cardiac complications. Coenzyme Q10 and L-carnitine supplementation are commonly used, though evidence for their efficacy remains limited. A multidisciplinary approach involving neurologists, cardiologists, audiologists, and rehabilitation specialists is essential for optimal care. Genetic counseling is important for affected families, keeping in mind the maternal inheritance pattern of mitochondrial DNA.

Common questions about MERRF