[Renal microscopic polyarteritis replaced by pericarditis with episodic increases in MPO-ANCA in a patient with systemic lupus erythematosus].

A 41-year-old female was admitted to our hospital with acute renal failure. The renal biopsy showed focal necrotizing crescentic glomerulonephritis, and her serology revealed a high titer of MPO-ANCA. The diagnosis of MPO-ANCA-associated microscopic polyarteritis was made, and her basic illness proved to be systemic lupus erythematosus (SLE) because of renal injury, polyarteritis, pancytopenia, anti-double-strand DNA antibody, and anti-nuclear antibodies. After treatment with prednisolone (PSL) and cyclophosphamide, her renal function improved and her MOP ANCA titer was lowered. After 2 years, she was readmitted due to dyspnea. Chest X-ray and echocardiography revealed pericarditis and bilateral pleural effusion. Renal biopsy was carried out again because of an increase in MPO-ANCA, which showed minor abnormalities. PSL therapy led to remission of pericarditis, resulting in a decrease in MPO-ANCA. In this case, MPO-ANCA is likely to be associated not with the activity of polyarteritis, but with that of SLE, and care should be taken in evaluating the clinical usefulness of MPO-ANCA in cases with SLE.