[Microscopic polyangitis with pleuritis as the only pulmonary complication]

A 75-year-old woman was admitted to our hospital because of high fever and appetite loss. A chest roentgenogram and computed tomographic scans revealed pleural effusion without obvious infitrative or interstitial shadows in both lung fields. Laboratory data showed microhematuria, proteinuria, and telescoped sediment with a moderate increase in C-reactive protein, suggestive of acute glomerulonephritis. Because infectious pleuritis, was initially suspected, the patient was treated with antibiotics. However, her general condition deteriorated, and the right pleural effusion increased. Levels of myeloperoxidase-specific anti-neutrophil cytoplasmic antibody (MPO-ANCA) in serum and pleural effusion were markedly elevated, yielding a conclusive diagnosis of MPO-ANCA-related vasculitis, especially microscopic polyangitis (MPA). The Patient was immediately treated treated with prednisolone, cyclophosphamide, and plasma exchange. Several weeks later, her general condition dramatically improved, and the level of MPO-ANCA in serum markedly decreased. In addition, the pleural effusion completely disappeared. Unfortunately, the patient eventually died of opportunistic infections (MRSA-pneumonia and Aspergillus-pneumonia) 6 months after admission. This was a unique case of MPA associated with pleuritis without interstitial pneumonia or alveolar hemorrhage.