Mitochondrial complex III deficiency
- Complex 3 mitochondrial respiratory chain deficiency
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The most severe form begins in infancy and causes life-threatening muscle and nervous system dysfunction (encephalomyopathy), lactic acidosis at birth, hypotonia (poor muscle tone), dystrophic posturing, seizures, and coma. Ragged-red fibers, a characteristic microscopic abnormality observed in muscle biopsy, are commonly present with this form.
In some individuals, encephalomyopathy does not begin until childhood or adulthood. For these individuals, symptoms may include various combinations of weakness, short stature, ataxia (inability to coordinate muscle movements), dementia, hearing loss, sensory neuropathy, pigmentary retinopathy (a disorder of the retina characterized by deposits of pigment and vision loss), and possible lactic acidosis or other features. Ragged-red fibers are common in these individuals as well.
Individuals with a less severe type may have myopathy with exercise intolerance that progresses to general weakness. Ragged-red fibers and lactic acidosis may be present.
A fourth described form is characterized by infantile histiocytoid cardiomyopathy. This is a condition characterized by cardiomegaly (enlarged heart), severe cardiac arrhythmias or sudden death, and the presence of histiocyte-like cells within the heart muscle.
- Facts About Mitochondrial Myopathies. Muscular Dystrophy Association. April 2010; http://www.mdausa.org/publications/mitochondrial_myopathies.html#whatare. Accessed 4/4/2011.
- Types of Mitochondrial Disease. United Mitochondrial Disease Foundation. http://www.umdf.org/site/c.otJVJ7MMIqE/b.5692881/k.4B7B/Types_of_Mitochondrial_Disease.htm#Complex3. Accessed 4/4/2011.
- Histiocytoid cardiomyopathy. Orphanet. May 2008; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=137675. Accessed 8/29/2011.