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Myoclonus with epilepsy with ragged red fibers

Other Names for this Disease
  • Fukuhara syndrome
  • Merrf syndrome
  • Myoclonic epilepsy associated with ragged-red fibers
  • Myoencephalopathy ragged-red fiber disease
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MERRF is a disorder characterized by myoclonus, which is often the first symptom, followed by generalized epilepsy, ataxia, weakness, and dementia.  Symptoms usually first appear in childhood after normal early development but symptoms can also first occur in adulthood.  Symptoms vary widely from individual to individual and the course may be slowly progressive or rapidly downhill.  Other common findings include hearing loss, short stature, optic atrophy, and cardiomyopathy with Wolff-Parkinson-White (WPW) syndrome.   The diagnosis is based on clinical features and a muscle biopsy finding of ragged red fibers (RRF) [1].  The condition is caused by mutations - that can be detected with genetic testing in 90% of affected individuals - in the mitochondrial gene called MT-TK.  The seizure disorder is treated with conventional anticonvulsant therapy.  Coenzyme Q10 and L-carnitine are often used in hopes of improving mitochondrial function.[2]
Last updated: 6/17/2008


  1. Seidman, Roberta. eMedicine. Muscle Biopsy and the Pathology of Skeletal Muscle. Nov 2, 2006; Accessed 6/16/2008.
  2. DiMauro, S. and Hirano, M. MERRF. GeneReviews. September 27, 2005; Accessed 6/16/2008.
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  • The Online Mendelian Inheritance in Man (OMIM) is an catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
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