MERRF syndrome

| Name           = MERRF syndrome | Image          = Ragged red fibers in MELAS.jpg|thumb | Caption        = Example of "ragged red fibers" in MELAS syndrome. | DiseasesDB     = 30794 | ICD10          = | ICD9           = | ICDO           = | OMIM           = 545000 | MedlinePlus    = | eMedicineSubj  = | eMedicineTopic = | MeshID         = D017243 }} 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 Europe, and has varying degrees of expressivity owing to heteroplasmy.
 * {Infobox disease

Presentation
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

Causes
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:


 * MT-TK


 * MT-TL1


 * MT-TH


 * MT-TS1


 * MT-TS2


 * MT-TF

Treatment
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.