[Mitochondrial insufficiency in children].

Structural and functional disturbances closely associated with mitochondrial insufficiency are found in the nervous system elements, skeletal and smooth muscles, myocardium, kidneys, liver, gastrointestinal tract, endocrine glands, systems of hematopoiesis and immunity. Nosological and syndromic forms of mitochondrial pathology associated with mitochondrial or nuclear DNA mutations are characterized. The disease variants with symptomatic (may be secondary) or with presumable mitochondrial pathology are analyzed. For the pathologist the most reliable diagnostic criteria are skeletal muscle changes, and the "ragged red fibres" phenomenon first of all. The comparisons of the clinicobiochemical and morphological data are of the decisive importance.