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cholesterol deposits

Saturday 28 January 2006

The cellular metabolism of cholesterol is tightly regulated such that most cells use cholesterol for the synthesis of cell membranes without intracellular accumulation of cholesterol or cholesterol esters. Accumulations, however, manifested histologically by intracellular vacuoles, are seen in several pathologic processes.

- atherosclerosis
- xanthomas

- In atherosclerotic plaques, smooth muscle cells and macrophages within the intimal layer of the aorta and large arteries are filled with lipid vacuoles, most of which are made up of cholesterol and cholesterol esters. Such cells have a foamy appearance (foam cells), and aggregates of them in the intima produce the yellow cholesterol-laden atheromas characteristic of this serious disorder. Some of these fat-laden cells rupture, releasing lipids into the extracellular space.

The extracellular cholesterol esters may crystallize in the shape of long needles, producing quite distinctive clefts in tissue sections.

- Xanthomas. Intracellular accumulation of cholesterol within macrophages is also characteristic of acquired and hereditary hyperlipidemic states. Clusters of foamy cells are found in the subepithelial connective tissue of the skin and in tendons, producing tumorous masses known as xanthomas.
Inflammation and necrosis.

Foamy macrophages are frequently found at sites of cell injury and inflammation, owing to phagocytosis of cholesterol from the membranes of injured cells, including parenchymal cells, leukocytes, and erythrocytes. Phospholipids and myelin figures are also found in inflammatory foci. When abundant, the cholesterol-laden macrophages impart a yellowish discoloration to such inflammatory foci.

- Cholesterolosis

This refers to the focal accumulations of cholesterol-laden macrophages in the lamina propria of the gallbladder (Fig. 1-37). The mechanism of accumulation is unknown.

- Niemann-Pick disease, type C

In this lysosomal storage disease, an enzyme involved in cholesterol trafficking is mutated, and hence cholesterol accumulates in multiple organs.