Maternally Inherited Leigh Syndrome and NARP Syndrome
National Organization for Rare Disorders, Inc.
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Maternally inherited Leigh syndrome (MILS) and neuropathy, ataxia and retinitis pigmentosa (NARP) syndrome are rare genetic multisystem disorders that are part of a spectrum or continuum of disease caused by abnormalities affecting mitochondrial energy production. NARP is characterized by nerve disease affecting the nerves outside of the central nervous system (peripheral neuropathy), an impaired ability to coordinate voluntary movements (ataxia), an eye condition known as retinitis pigmentosa (RP), and a variety of additional abnormalities. MILS is generally a more severe mitochondrial disorder that often becomes apparent during infancy or childhood and is characterized by brain disease (encephalopathy), elevated levels of lactic acid in the body (lactic acidosis), seizures, heart disease (cardiomyopathy), breathing (respiratory) abnormalities, and developmental delays. The specific symptoms and severity of these disorders in each individual can vary greatly from one person to another and even among members of the same family.
MILS and NARP syndrome are maternally inherited mitochondrial disorders. They are caused by specific mutations affecting the mitochondrial gene known as the ATPase 6 gene. When individuals have more than 90 percent of mutated mitochondrial DNA (mtDNA) in their cells, they are classified as having MILS and not NARP syndrome. Most individuals with NARP syndrome have 70-80 percent of mutated mtDNA. In some families, one individual may have NARP syndrome while another individual is diagnosed with MILS. (For more information on mtDNA see the Causes section below.)
Mitochondrial disorders are characterized by mutations affecting the parts of the cell that release energy (mitochondria). Mitochondrial diseases often hamper the ability of affected cells to break down food and oxygen and produce energy. In most mitochondrial disorders, abnormally high numbers of defective mitochondria are present in the cells of the body. Mitochondrial diseases often affect more than one organ system of the body. NARP syndrome was first identified in the medical literature in 1990. Leigh syndrome was first reported in the medical literature in 1951.
CLIMB (Children Living with Inherited Metabolic Diseases)
176 Nantwich Road
Crewe, CW2 6BG
United Mitochondrial Disease Foundation
8085 Saltsburg Road Suite 201
Pittsburgh, PA 15239
Retinitis Pigmentosa International
P.O. Box 900
Woodland Hills, CA 91365
NIH/National Institute of Neurological Disorders and Stroke
P.O. Box 5801
Bethesda, MD 20824
Mitochondrial Disease Support Group Online (Deleted)
5022 Michigan Avenue
West Palm Beach, FL 33415
Children's Mitochondrial Disease Network
30 Heber Walk
England, CW9 5JB
Mitochondria Research Society
Department of Cancer Genetics
Roswell Park Cancer Institute
BLSC Building, Room # 3-316
Elm and Carlton Streets
Buffalo, NY 14221
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
14 Pembroke Street
Medford, MA 02155
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Last Updated: 1/31/2013
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