Prompt plasmapheresis successfully rescue pulmonary-renal syndrome caused by ANCA-negative microscopic polyangiitis.

Pulmonary-renal syndrome (PRS) associated with antineutrophil cytoplasmic antibodies (ANCA)-negative microscopic polyangiitis (MPA) is relatively rare, and the effects of plasmapheresis on these patients remain unclear. Here, we report the case of a 66-year-old man who presented with fever, acute renal failure, thrombocytopenia, and sudden onset of diffuse pulmonary hemorrhage. Prompt plasmapheresis and concurrent pulse therapy with methylprednisolone effectively rescued his pulmonary-renal syndrome. The patient was then diagnosed with MPA on the basis of typical histological findings and the absence of surrogate markers of Wegener's granulomatosis and Churg-Strauss syndrome. This case demonstrates the therapeutic effects of plasmapheresis on ANCA-negative MPA and highlights the necessity of prompt plasmapheresis for not only resolving pulmonary hemorrhage but also increasing the likelihood of renal function restoration in patients with PRS.