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What has caused this man in his 20s with obesity to develop raised reddish-yellow bumps on his back, shoulders, and the extensor surfaces of his arms and legs? That's the question facing Jun Li, MD, of Peking Union Medical College Hospital in Beijing, and colleagues, as reported in .

The patient explained that he had developed the rash about 2 years previously, but it had not been itchy or painful. The patient's body mass index was 31.2. He noted a tendency to eat fatty foods. On taking his history, clinicians learned that he had been living with uncontrolled diabetes for some time. He said he was not aware of any family history of dyslipidemia, metabolic syndrome, vascular disease, pancreatitis, or skin diseases.

Physical examination revealed widespread dome-shaped yellow papules that were firm to the touch. They were scattered symmetrically across his back, shoulders, arms, thighs, and knees.

Results of lab tests showed that the patient had significant elevations in triglycerides (6,697 mg/dL) and total cholesterol (943 mg/dL), and a low level of high-density lipoprotein cholesterol (0.016 mg/dL).

Histopathologic examination revealed "large, pale-staining, lipid-laden histiocytes (foamy cells) and obvious loose lipids in the upper dermis that were consistent with an ," Li and team wrote.

This form of xanthoma generally develops as groups of small, reddish-yellow papules, usually affecting the trunk, buttocks, and the extensor surfaces of the arms and legs. In the early stage of development, lesions are tender and surrounded by an erythematous halo that is itchy, tender, and produces a burning sensation. Eruptive xanthoma is diagnosed clinically, particularly in people with risk factors, the group noted.

Differential diagnoses for eruptive xanthoma include:

• Molluscum contagiosum
• Langerhans cell histiocytosis
• Non–Langerhans cell histiocytosis
• Sebaceous hyperplasia
• Disseminated granuloma annulare
• Nodular basal cell carcinoma

Eruptive xanthoma can be differentiated from these similar conditions based on findings of skin biopsies showing foam cells (i.e., lipidized macrophages), with extracellular lipid deposits and perivascular inflammatory infiltration, Li and colleagues explained.

Eruptive xanthoma occurs in the presence of significant hypertriglyceridemia, with levels that often exceed 3,000 mg/dL, they added. This is typically accompanied by polygenetic factors and comorbidities, including poorly controlled/untreated diabetes; patients may also have obesity and sedentary lifestyles, be excessive consumers of alcohol and carbohydrates, and may be taking medications to address other conditions.

However, primary is also a typical feature of the rare monogenic disorder, familial lipoprotein lipase deficiency, which tends to present during childhood, with early onset of eruptive xanthomas, lipemia retinalis, enlargement of the liver and spleen, and recurrent abdominal pain.

Diagnosis and management of this monogenic condition may be assisted by genetic testing, Li and colleagues noted. Regardless of its cause, severe hypertriglyceridemia should be addressed by following a very-low-fat diet, reducing consumption of refined carbohydrates, and limiting or completely avoiding alcohol. Beyond these lifestyle modifications, "drugs such as fibrates, niacin, high doses of omega-3 fatty acids, or even some novel therapies like apolipoprotein C-III antisense, are associated with decreased levels of triglycerides," the authors wrote.

Secondary factors must also be addressed, they emphasized. "Prompt admission to the hospital is critical to preventing life-threatening conditions like hyperlipidemic pancreatitis, diabetic ketoacidosis, and coronary artery diseases," they noted. Skin lesions generally abate on their own over several weeks or months, once normal plasma triglyceride levels are restored.

In this patient's case, they did not order genetic testing given his age when the skin lesions developed, the multiple contributing factors, the absence of family history, and test costs.

The team prescribed simvastatin and referred the patient to endocrinology immediately for further assessment and treatment of his hyperglycemia and hypertriglyceridemia.

At that point, he was lost to follow-up, until 1 year later, when he was hospitalized with acute pancreatitis. Strict management of his glycemic and lipid levels achieved control over his systemic complications, and the xanthoma gradually disappeared. At 8-year follow-up, the patient's condition was stable.

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