Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 40-year-old man is evaluated for a new skin rash of 10 days’ duration. The rash appeared abruptly and is not tender or pruritic. The patient has poorly controlled type 2 diabetes mellitus. His current medications include metformin and glyburide. Family history is unremarkable.

On physical examination, vital signs are normal. BMI is 25. There are several grouped 1- to 5-mm yellow papules on extensor surfaces of extremities and buttocks. Some of the papules have surrounding erythema. The remainder of the examination is normal.

Laboratory studies show an HbA1c value of 12%.

Which of the following disorders is associated with the patient’s skin findings?

A. Familial dysbetalipoproteinemia
B. Familial hypercholesterolemia
C. Hypertriglyceridemia
D. No underlying disorder

MKSAP Answer and Critique

The correct answer is C. Hypertriglyceridemia.

This patient has eruptive xanthomas, which are characterized by a rapid onset of numerous yellow papules with surrounding erythema found primarily on the extensor surfaces of the extremities and buttocks. Xanthomas are localized lipid deposits whose presence is suggested by characteristic cutaneous papules, plaques, or nodules.

Cutaneous xanthomas can be idiopathic and not associated with an underlying disorder or an indication of a primary dyslipidemia, hyperlipidemia secondary to another disorder, medication effect (estrogens, prednisone, protease inhibitors), or hematologic disease. The ability to diagnose the xanthoma subtype will direct the proper testing and treatment. When necessary, diagnosis can be confirmed with a skin biopsy that shows lipid-laden macrophages in the dermis. Eruptive xanthomas are pathognomonic of hypertriglyceridemia, and a vast number of these patients also have a diagnosis of diabetes mellitus. Eruptive xanthomas have also been reported as a complication of hypertriglyceridemia-induced pancreatitis.

Tuberous xanthomas are associated with markedly elevated low-density lipoprotein levels (familial hypercholesterolemia) and elevated intermediate-density lipoprotein and triglyceride levels (familial dysbetalipoproteinemia). Tuberous xanthomas present as yellow to red papules or nodules up to 3 cm in size located over joints and extensor surfaces of the elbows and knees. The location and size of tuberous xanthomas distinguish them from eruptive xanthomas.

Tendinous xanthomas are skin-colored nodules most commonly located over the Achilles tendon. They are smooth, firm, and mobile and are attached to and move with the tendon. Tendon xanthomas are typically associated with familial hypercholesterolemia and familial defective apo B-100. The location, size, and color of these tumors distinguish them from eruptive xanthomas.

Plane xanthomas may occur in the absence of lipid disorders in approximately 50% of adults or can be associated with familial dysbetalipoproteinemia, homozygous familial hypercholesterolemia, and hypercholesteremia associated with primary biliary cirrhosis. Plane xanthomas are recognized as yellow thin plaques most commonly found around the eyelids (xanthelasma), neck, trunk, shoulders, axillae, and in some cases, palms. The flat plaque-like appearance and location of plane xanthomas distinguishes them from eruptive xanthomas.

Key Point

• Eruptive xanthomas, characterized by yellow papules with surrounding erythema, are pathognomonic of hypertriglyceridemia, with a number of these patients also having a diagnosis of diabetes mellitus.

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