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Diseases Studied

The Rare Diseases Clinical Research Network is an NIH-funded research network of 20 active consortia or research groups working to advance treatment for diseases that are rare. Use the search tools on this page to find the diseases we currently study. You can reach out to the indicated consortia or research groups for more information on those diseases and studies underway.

This network focuses on clinical research and does not generally support clinical care outside of research activities. To learn about other rare diseases, please visit the Genetic and Rare Diseases Information Center (GARD), which is an NIH program that helps the public find reliable information about rare and genetic diseases. Their staff are specialists. Contact them at 1-888-205-2311 or email

All Diseases > Myoclonus epilepsy ragged-red fibers

Myoclonus epilepsy ragged-red fibers (MERRF)

Alternative Names: Fukuhara Disease; MERRF Syndrome; Myoclonic Epilepsy Associated with Ragged-Red Fibers; Myoencephalopathy Ragged-Red Fiber Disease

Disease Category: Mitochondrial Disorders

A rare, multisystemic disorder affecting the nervous system and muscles. Symptoms include myoclonus (muscle twitches), muscle weakness, seizures, spasticity (muscle rigidity), ataxia (lack of coordination), peripheral neuropathy (sensory changes and muscle weakness in the extremities), intellectual deficits, optic nerve atrophy (wasting), short stature, cardiomyopathy (heart disease), and, less commonly, lipomas (fatty tumors under the skin). Muscle cells from affected individuals reveal abnormal "ragged-red" muscle fibers with a special stain and viewed under a microscope.

Research groups studying this disease

Mitochondrial Disorders
NAMDC logo

North American Mitochondrial Disease Consortium (NAMDC)

Improves quality of life for people affected by mitochondrial disease through education, outreach, advocacy, and clinical research initiatives.

Promotes research and education for the diagnosis, treatment, and cure of mitochondrial disorders while providing support to those affected.