[Serum amyloid protein A was a useful marker for steroid tapering in a case of MPO-ANCA-associated vasculitis].

A 55-year-old man was admitted complaining of hemosputa, fever and dyspnea. The chest radiographs and computed tomography showed a diffuse alveolar filling pattern; suggesting alveolar hemorrhage. Laboratory data demonstrated renal dysfunction with hematuria and proteinuria and serum MPO-ANCA was also elevated. Respiratory failure progressed rapidly within two days. Steroid pulse therapy and plasmapheresis was performed. Thereafter, symptoms and chest radiograph findings improved dramatically. However proteinuria persisted as steroid administration was tapered. Renal biopsy demonstrated gromeluronephritis and interstitial lymphocyte infiltration. After administering a second course of steroid semi-pulse therapy, her proteinuria improved. C-reactive protein and MPO-ANCA decreased to normal levels after the initial steroid therapy, but serum amyloid A protein (SAA) gradually elevated. The second course of steroid pulse therapy normalized SAA, and proteinuria improved. Based on these findings, SAA seems to be a more sensitive marker for steroid tapering than either CRP or MPO-ANCA.