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The mitochondrial myopathies are a rare group of conditions affecting the respiratory chain and oxidative phosphorylation. A total of five protein complexes make up the mitochondrial electron transport chain. The clinical consequences of a deficiency in their normal physiology is associated with numerous syndromes as described in this section and presented in this book. Because of the complexity of this group of diseases, an overview is presented here, followed by a short description of the five individual deficiencies. Table C-2 lists the names of the associated medical disorders that are described as specific syndromes in this book.

Complex Deficiency

Graphic illustration of the electron transfer chain within the mitochondrium and corresponding clinical disorders. COX, cytochrome C oxidase deficiency; FIEM, fatal infantile encephalomyopathy; LHON, Leber hereditary optic atrophy; LS, Leigh syndrome; MELAS, mitochondrial encephalomyopathy-lactic acidosis-stroke syndrome; MERRF, myoclonus epilepsy ragged-red fibers; MNGIE, mitochondrial neurogastrointestinal encephalopathy syndrome; KSS, Kearns-Sayre syndrome; PEO, progressive external ophthalmoplegia.

Table C-2 Mitochondrial Respiratory Chain Composition by Complex

“Mitochondrial medicine” was defined by Luft and Moyan-Hughes in the late 1980s and became the subject of numerous investigations of the metabolic disorders affecting the muscles and the brain. Mitochondria were first recognized in 1898 by Bend. The term comes from the Greek mitos (thread) and chondros (grain). The concept of cellular respiration was defined and studied in the 1920s.

In the 1970s and mid-1980s, the standard classification of respiratory chain disorders rested ...

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