Case of Classic Polyarteritis Nodosa Resembling Lupus Nephritis

Classic polyarteritis nodosa (cPAN) is a systemic necrotizing vasculitis of medium-sized muscular arteries. Glomerular involvement is not expected in the course of cPAN. Herein, we describe a case of cPAN with glomerular and multiple arterial involvement. The patient presented with severe abdominal pain and high fever. Urine analysis showed hematuria and 1g/day proteinuria. Kidney biopsy showed fibrinoid necrosis of arterioles and IgG, IgA and C1q positivity raising a suspicion of lupus nephritis. However digital subtraction angiography revealed typical multiple micro-aneurysms in the coronary, mesenteric, splenic and renal arteries establishing the diagnosis of cPAN. Kidney biopsy in cPAN may reveal non-specific immune-deposits and fibrinoid necrosis of arterioles mimicking lupus nephritis and microscopic polyangiitis. c-PAN should be carefully differentiated from these entities.