Example of "ragged red fibers" in MELAS syndrome.
|Classification and external resources|
MERRF syndrome (or myoclonic epilepsy with ragged red fibers) is a mitochondrial disease. It is extremely rare, with an estimated prevalence of 1/400,000 in Northern Europe, and has varying degrees of expressivity owing to heteroplasmy.
It involves the following characteristics:
- progressive myoclonic epilepsy
- "Ragged Red Fibers" - clumps of diseased mitochondria accumulate in the subsarcolemmal region of the muscle fiber and appear as "Ragged Red Fibers" when muscle is stained with modified Gömöri trichrome stain
- short stature
- hearing loss
- lactic acidosis
- exercise intolerance
- poor night vision
The MERRF syndrome is caused by a maternally-inherited mutation at position 8344 in the mitochondrial genome in over 80% of cases. This point mutation disrupts the mitochondrial gene for tRNA-Lys and so disrupts synthesis of proteins essential for oxidative phosphorylation.
Many genes are involved. These include:
Like many mitochondrial diseases, there is no cure for MERRF and treatment is primarily symptomatic. High doses of Coenzyme Q10 and L-Carnitine have been tried with little success as therapies in hopes of improving mitochondrial function.
- Gene Reviews: MERRF
- Online Mendelian Inheritance in Man (OMIM) MYOCLONIC EPILEPSY ASSOCIATED WITH RAGGED-RED FIBERS; MERRF -545000
- Zeviani M, Muntoni F, Savarese N, et al. (1993). "A MERRF/MELAS overlap syndrome associated with a new point mutation in the mitochondrial DNA tRNA(Lys) gene". Eur. J. Hum. Genet. 1 (1): 80–7. PMID 8069654.
- Melone MA, Tessa A, Petrini S, et al. (February 2004). "Revelation of a new mitochondrial DNA mutation (G12147A) in a MELAS/MERFF phenotype". Arch. Neurol. 61 (2): 269–72. doi:10.1001/archneur.61.2.269. PMID 14967777.
- Nakamura M, Nakano S, Goto Y, et al. (September 1995). "A novel point mutation in the mitochondrial tRNA(Ser(UCN)) gene detected in a family with MERRF/MELAS overlap syndrome". Biochem. Biophys. Res. Commun. 214 (1): 86–93. doi:10.1006/bbrc.1995.2260. PMID 7669057.
- Mancuso M, Filosto M, Mootha VK, et al. (June 2004). "A novel mitochondrial tRNAPhe mutation causes MERRF syndrome". Neurology. 62 (11): 2119–21. doi:10.1212/01.wnl.0000127608.48406.f1. PMID 15184630.
- Gene reviews: MERRF: Management of patients