Steatosis

STEATOSIS (from Greek stear- fat, grease), a term sometimes used to denote exogenous obesity, fatty infiltration (see Fatty degeneration) and contrasted with myelinosis, i.e., fatty decomposition. According to the chemical nature of the fatty substances infiltrating tissues, steatosis can be: glycerin-ester, cholesterol, and lipoid. By method of formation, steatosis can be distinguished as that from increased delivery of nutrients to tissues and from disturbance of tissue metabolism. The first type includes: steatosis from enhanced feeding, which has a physiological character within certain limits and is reversible; steatosis with increased transport of fat from fat depots; resorptive steatosis (during resorption of necrotic tissues, exudates, etc.); the second type includes steatosis in cellular dystrophies (degenerative obesity). Sometimes steatosis also arises apparently from a primary increase in the ability of cells to accumulate fat due to unknown disturbances in intracellular metabolism (e.g., in true xanthomas). Finally, metabolic steatosis in some general exchange diseases (e.g., in diabetes) and steatosis due to decreased oxidation processes in the body (e.g., in anemias) are also distinguished. According to the localization of fat deposits, cellular steatosis and interstitial steatosis are differentiated. The latter mostly belong to cholesterol-steatoses and are particularly expressed in the walls of arteries and heart valves in atherosclerosis, in renal papillae, cornea of the eye (senile arcus), tendons, and other areas composed of dense fibro-elastic tissue.