Microscopic Polyangiitis Presenting as Membranoproliferative Glomerulonephritis

Microscopic polyangiitis (MPA) is characterized by pauci-immune necrotizing small vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation. The kidney is the most often affected organ in the majority of patients with MPA, and renal manifestations are usually the first symptoms. Glomerular capillaries are affected most often, resulting in necrotizing glomerulonephritis, usually in a crescent formation, with no or few immune deposits able to be demonstrated at the sites of vasculitis and glomerulonephritis. We report a case of microscopic polyangiitis in both legs with pitting edema in a 50-year-old female. Laboratory findings showed hematuria, proteinuria, and a positive peripheral antineutrophil cytoplasmic antibody. A renal biopsy revealed pauci-immune splitting and necrotizing capillary loop walls necrotizing vasculitis and membranoproliferative glomerulonephritis (MPGN). With a diagnosis of MPA, she has been managed with high dose steroid and cyclophosphamide. To our knowledge, this is the first reported case of MPA with MPGN.