AssessmentsVasculitis: Pathology review
USMLE® Step 1 style questions USMLE
A 52-year-old man comes to the clinic due to fatigue, joint pain, and recent appearance of skin lesions on his legs. His medical history is noncontributory except for a car accident as a child which required hospitalization and multiple blood transfusions. He has not seen a physician in more than 10 years. The patient does not use tobacco, alcohol or illicit drugs. He is monogamous with one sexual partner. Temperature is 37.0°C (98.6°F), pulse is 75/min, and blood pressure is 130/85 mmHg. Physical exam shows purpuric papules covering the lower extremities that do not blanch with pressure. The rest of the physical examination is unremarkable. Laboratory tests are obtained and shown below:
Urinalysis is unremarkable. Serum protein electrophoresis and immunofixation reveals polyclonal IgG and monoclonal IgM bands. Testing for cryoglobulins shows no precipitation after 24 hours. Which of the following tests is most likely to reveal this patient's underlying condition?