Lipid deposition in human tendon xanthoma

Tendon xanthomas often accompany the rapidly progressive atherosclerosis that develops in patients with familial hypercholesterolemia. This report describes lipid accumulation, as studied histochemically, in an Achilles tendon xanthoma from a patient whose death was secondary to complications of familial hypercholesterolemia. Lipid was stained with oil red O and filipin dyes for detection of esterified and unesterified cholesterol, respectively. As in human atherosclerosis, unesterified cholesterol accumulated in the tendon predominantly in the extracellular space but separately from oil-red-O-stained lipid that accumulated both intra- and extracellularly. Deposition of unesterified cholesterol in human atherosclerotic lesions and tendon xanthomas is an interesting but as yet unexplained phenomenon.