[A case of microscopic polyarteritis nodosa associated with myeloperoxidase-antineutrophil cytoplasmic autoantibodies (MPO-ANCA)].

We report a case of microscopic polyarteritis nodosa associated with myeloperoxidase-antineutrophil cytoplasmic autoantibodies (MPO-ANCA). A 38 year-old female was admitted to our hospital, because of proteinuria, recurrent pyrexia, polyarthralgia, abdominal pain and purpura. She had a history of severe pulmonary hemorrhage and 4 kg weight loss for 8 months. On admission perinuclear ANCA without cytoplasmic ANCA was detected by indirect immunofluorescence assay and MPO-ANCA was detected by enzyme linked immunosorbent assay. But anti-nuclear antibodies, immune complexes and anti-glomerular basement membrane antibodies were not detected. Renal biopsy showed necrotizing crescentic glomerulonephritis without immune deposits. Skin biopsy revealed leukocytoclastic vasculitis. Diagnosis of microscopic polyarteritis nodosa was made by these clinical and histological evidence of vasculitis. As renal failure progressed after admission, corticosteroid and cyclophosphamide administration were started. Renal function and other symptoms improved paralleled with decreased MPO-ANCA titer to normal values. It is suggested that MPO-ANCA may be closely related to the pathogenesis of microscopic polyarteritis nodosa and it may be a good serological marker for diagnosis and disease activity of this disease.