Mitochondrial myopathy

A form of muscle disease that leads to progressive muscle weakness. More than 25 types of enzyme abnormalities have been defined that fall into this category. They result in a disease of cell metabolism and are defined by a biopsy of muscle tissue that shows “ragged-red fibers” under microscopic examination.

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any of a group of myopathies associated with an increased number of enlarged, often abnormal, mitochondria in muscle fibers, manifested by exercise intolerance, generalized weakness, lactic acidosis, infantile quadriparesis, ophthalmoplegia, and cardiac abnormalities. Underlying metabolic defects include defects in substrate utilization, defects in the coupling of mitochondrial respiration to phosphorylation, and deficiencies in mitochondrial respiratory chain components.