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.