The lipid composition and localization of free and esterified cholesterol in different types of xanthomas.

The lipid composition of 17 xanthomatous lesions from 16 patients with different types of hyperlipoproteinaemia was analyzed. The relative amounts of free cholesterol, cholesterolesters, and phospholipids in xanthomas obtained from patients who subsequently showed regression of their remaining type of xanthomas were different in comparison with xanthomas which did not show regression. One tendinous xanthoma contained more than 50% free cholesterol and resembled in lipid composition the gruel plaques found in atherosclerotic lesions. The relative amounts of free cholesterol, cholesterolesters, and phospholipids in regressing xanthomas were similar to those of fatty streaks found in arteries of children between the ages of 5-10 yr. Histochemical studies using an enzymatic method demonstrated that free and esterified cholesterol were located in focal areas of xanthomatous tissue. It is concluded that the physical state of lipids in xanthomatous lesions can vary remarkably and plays an important role with regard to the possibility of regression.