Xanthomas
Basics
Abnormalities of lipid metabolism, with high circulating levels of various lipoproteins can result in deposition of cholesterol and other lipids in the skin, tendons, and other organs.
Xanthomas consist of the lipids found in tissue macrophages in the skin and tendons. Lipoprotein abnormalities have been classified into primary (genetic) lipoproteinemia and secondary lipoproteinemia resulting from underlying diseases.
There is also a high correlation between abnormal lipoproteinemia and the development of atherosclerosis.
Primary lipoproteinemias are phenotypic expressions of various genetic disorders of lipid metabolism with the following characteristics:
Type I, familial lipoprotein lipase deficiency: elevated chylomicrons
Type IIA, familial hypercholesterolemia: elevated low-density lipoproteins
Type IIB, familial hyperlipidemia: elevated low-density lipoproteins and very-low-density lipoproteins
Type III, familial dysbetalipoproteinemia: elevated intermediate-density lipoproteins
Type IV, endogenous familial hypertriglyceridemia: elevated triglycerides
Type V, familial combined hyperlipidemia: elevated chylomicrons and elevated very-low-density lipoproteins
Secondary hyperlipoproteinemias result from disturbances in cholesterol and triglyceride metabolism caused by cholestatic liver disease, diabetes mellitus, pancreatitis, multiple myeloma, and nephrotic syndrome. These disorders may mimic any of the genetic lipoprotein abnormalities and may produce similar xanthomatous deposits in tissues.
Clinical Variants
Smooth, yellow, papular lesions (2 to 5 mm) (Fig. 34.11A,B). Sometimes a red halo appears around the lesions.
Appear suddenly over the extensor surfaces and pressure points (Fig. 34.12).
These lesions are usually seen in association with very high levels of triglycerides (2,000 to 4,000 mg/dL). Uncontrolled diabetes mellitus and acute pancreatitis are both common underlying causes of their surfacing on the skin.
Also known as xanthoma palpebrarum, xanthelasma is a form of planar xanthoma (Fig. 34.13).
Lesions grow slowly over years. More than 50% of patients with xanthelasma have normal lipoprotein levels.
Small (0.5 cm) to large (3 to 5 cm), firm, yellow papules and nodules (Fig. 34.14).
Lesions are also slow growing. They are associated with familial hypercholesterolemia but can also occur in patients with high triglyceride levels.
Distribution of Lesions
Eruptive xanthomas appear most frequently over the knees, elbows, and buttocks.
Planar xanthomas are found in the palmar creases but may also be generalized.
Xanthelasma lesions are usually found on the eyelids and medial canthus.
Tuberous xanthomas are found on the elbows, knees, and buttocks.
Tendinous xanthomas affect the Achilles tendon, extensor tendons of the wrists, elbows, and knees.
Laboratory Evaluation
Fasting blood levels of triglycerides and cholesterol should be determined.
Lipoprotein electrophoresis demonstrates specific lipoprotein abnormalities.
Skin biopsy of xanthomas demonstrates collections of lipids in foamy macrophages in the dermis.
Serum glucose levels and glycosylated hemoglobin A1C are determined to rule out diabetes mellitus.
Serum amylase levels should be examined to rule out pancreatitis.
Serum protein electrophoresis should be performed to rule out multiple myeloma.
Differential Diagnosis
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Management