A 47-year-old man with eruptions on his trunk

A 47-year-old white male came to the hospital emergency department complaining of chest pain. At admission, it was noted that the patient had numerous lesions on his buttocks, abdomen, back, and all extremities. These lesions had been there for approximately 5 months--they developed after he discontinued his cholesterol medication due to lapsed insurance coverage. He had a similar eruption when he went off cholesterol medication on another occasion. The patient's medical history included type 2 diabetes mellitus, hypertension, coronary artery disease, and hyperlipidemia. He has had multiple heart catheterizations with stent placement, most recently 2 years ago. His mother also had diabetes mellitus, and she died at age 58 from a myocardial infarction. On examination, his lesions were painless and nonpruritic. He had numerous yellow papules on his buttocks, abdomen, back, and upper and lower extremities. He had no lesions on his face. The rest of the physical exam showed no abnormal results. What is your diagnosis? What laboratory tests should be done to help make the diagnosis?