A 55-year-old woman has had several weeks of fever, abdominal pain, weight loss, and lack of energy. Three days prior to the assessment, she developed a left foot drop. Her blood pressure is 160/90 mm Hg, pulse 80/min, and physical examination confirms left peroneal nerve damage and a bilateral sensory peripheral neuropathy in both legs. There are no skin rashes. Laboratory evaluation reveals ESR of 105 mm/h, WBC of 14,000/mL, and negative serologic tests for antineutrophil cytoplasmic antibody (ANCA) and ANA. The eosinophil count is normal, and urinalysis is negative for casts, protein, and red cells. Which of the following is the most likely mechanism for renal injury in this condition?
High-Yield Explanation
This patient has polyarteritis nodosa (PAN) and in classic PAN, unlike microscopic polyangiitis, both small and medium vessels are involved. The renal lesions are ischemic secondary to fibrinoid necrosis of the vessels. In microscopic polyangiitis, a diffuse glomerulonephritis is frequently present. The most common organ systems involved are the kidneys, musculoskeletal system, and peripheral nervous system.