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Xanthomas
Cutaneous xanthomas are yellow-brown, pinkish, or orange macules, papules, plaques, nodules, or infiltrations in tendons. They are
characterized histologically by accumulations of xanthoma cells—macrophages containing droplets of lipids. Xanthomas may be
symptoms of a general metabolic disease, a generalized histiocytosis, or a local fat phagocytosing storage process. The classification
of metabolic xanthomas is based on this principle: (1) xanthomas due to hyperlipidemia and (2) normolipidemic xanthomas. The
cause of xanthomas in the first group may be a primary hyperlipidemia, mostly genetically determined (Table 15-1), or secondary
hyperlipidemia, associated with certain internal diseases such as biliary cirrhosis, diabetes mellitus, chronic renal failure, alcoholism,
hyperthyroidism, and monoclonal gammopathy, or with intake of certain drugs such as beta-blockers and estrogens.
NOTE: TG, triglycerides; C, cholesterol; CM, chylomicrons; HDL, high-density lipoproteins; LDL, low-density lipoproteins; VLDL, very
low density lipoproteins; IDL, intermediate-density lipoproteins; +, raised; –, lowered.
Some of the xanthomas are associated with high plasma low-density lipoprotein (LDL)-cholesterol levels, and therefore with a
serious risk of atheromatosis and myocardial infarction. For that reason laboratory investigation of plasma lipid levels is always
necessary. In some cases an apoprotein deficiency is present. Table 15-2 shows correlations of clinical xanthoma type and
lipoprotein disturbances.
Xanthelasma
Most common of all xanthomas. In most cases an isolated finding unrelated to hyperlipidemia. Occurs in individuals >50 years;
however, when in children or young adults, it is associated with familial hypercholesterolemia (FH) or familial dysbetalipidemia (FD).
Synonyms: Xanthelasma palpebrarum, periocular xanthoma.
Skin lesions are asymptomatic. Soft, polygonal yellow-orange papules and plaques localized to upper and lower eyelids (Fig. 15-12)
and around inner canthus. Slow enlargement from tiny spots over months to years.
Xanthoma Tendineum
These subcutaneous tumors are yellow or skin-colored and move with the extensor tendons (Fig. 15-13). They are a symptom of
familial hypercholesterolemia (FH) that presents as type IIa hyperlipidemia. This condition is autosomal recessive with a different
phenotype in the heterozygote and homozygote. In the homozygote, the xanthomata appear in early childhood and the
cardiovascular complications in early adolescence; the elevation of the LDL content of the plasma is extreme. These patients rarely
attain ages above 20 years