[Mitochondrial diseases. Part I -- general review].

Inborn mitochondrial diseases (MD) may result from molecular defects involving the mitochondrial or the nuclear genome, so they may be transmitted maternally or as Mendelian traits; some cases occur sporadically. Numerous secondary causes of mitochondrial disorders are also known. Impairment of mitochondrial oxidation leads to the defective energy production, and further, to cellular damage. MD should be suspected when progressive signs occur, especially involving nervous system and muscles; other organs as heart, liver and kidney may also be affected.