MPO-ANCA- and IgA-positive systemic vasculitis: a possibly overlapping syndrome of microscopic polyangiitis and Henoch-Schoenlein purpura.

Microscopic polyangiitis (MPA) can be distinguished from Henoch-Schoenlein purpura (HSP) based on the presence of renal-pulmonary complications, myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) seropositivity and pauci-immune glomerulonephritis; these characteristics of MPA are generally not found in HSP. Here, we present a unique case with MPA and HSP overlapping syndrome. A 74-year-old man presented with a skin rash accompanied by intracranial bleeding, acute renal failure and pulmonary hemorrhage resulting in a fatal outcome. An autopsy revealed the marked formation of crescentic glomerulonephritis, diffuse pulmonary alveolar hemorrhage and focal cerebral bleeding. Histological features showing both dermal small-vessel vasculitis and cutaneous polyarteritis nodosa-like arteritis suggested MPA rather than HSP, in which the dermal small vessels are exclusively affected. Meanwhile, capillary immunoglobulin (Ig)A deposits in the skin and glomeruli suggested HSP. As MPA and HSP overlapping syndrome characterized by the synergistic effect of MPO-ANCA and the IgA immune complex may result in a fatal outcome, aggressive immunosuppressive therapy should be initiated as early as possible.