MEDizzy - A 43-year-old man has experienced malaise, fever, and a 4-kg

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Blood Vessels

A 43-year-old man has experienced malaise, fever, and a 4-kg weight loss over the past month. On physical examination, his blood pressure is 145/90 mm Hg, and he has mild diffuse abdominal pain, but no masses or hepatosplenomegaly. Laboratory studies include a serum urea nitrogen concentration of 58 mg/dL and a serum creatinine level of 6.7 mg/dL. Renal angiography shows right renal arterial thrombosis, and the left renal artery and branches show segmental luminal narrowing with focal aneurysmal dilation. During hemodialysis 1 week later, he experiences abdominal pain and diarrhea and is found to have melena. Which of the following serologic laboratory test findings is most likely to be positive in this patient?

ExplanationClassic polyarteritis nodosa (PAN) has segmental involvement of medium-sized arteries with aneurysmal dilation in the renal and mesenteric vascular beds (e.g., abdominal pain, melena). PAN can affect many organs at different times. Although the cause of PAN is unknown, about 30% of patients have hepatitis B surface antigen that presumably forms immune complexes that damage vascular walls. In contrast to microscopic polyangiitis, PAN has less of an association with anti–neutrophil cytoplasmic autoantibody (ANCA). A collagen vascular disease with a positive ANA test result, such as systemic lupus erythematosus, may produce a vasculitis, but not in the pattern seen here; the affected vessels are smaller. Vasculitis with HIV infection is uncommon.