Mitochondrial myopathy is a genetic disorder that affects the mitochondria, the "power plants" of cells. Mitochondrial myopathy is also known as mitochondrial disease, mitochondrial disorder, or simply mitochondrial dysfunction. Other synonyms for mitochondrial myopathy include mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); myoclonic epilepsy with ragged red fibers (MERRF); and Kearns-Sayre syndrome (KSS). The symptoms of mitochondrial myopathy can vary widely depending on the specific type of disorder that a patient has, but they often include muscle weakness, difficulty breathing, and fatigue. There is currently no cure for mitochondrial myopathy, but treatment options are available to manage symptoms and improve quality of life.