THIRD EDITION
Factsheet
Condition:
MERRF (myoclonic epilepsy with ragged-red fibers)
Inheritance:
Mitochondrial (maternal transmission)
Genetic Etiology:
Mutation in MT-TK gene encoding mitochondrial tRNA lysine
Frequency:
Approximately 1/400,000
Clinical features:
MERRF is a highly variable disorder that affects energy metabolism in multiple tissues. Onset is most commonly in childhood, with myoclonus, generalized seizures, ataxia, weakness, and dementia.
Management:
Supportive care; administration of coenzyme Q10 and L-carnitine.
Genetic counseling:
Follows pattern of maternal transmission, but with widely variable expression due to heteroplasmy. Molecular genetic testing is available.