[Case of microscopic polyangiitis presenting initially as prostatic vasculitis].

A 79-year-old man was admitted to our hospital to evaluate prostatic vasculitis that was diagnosed on a prostatic biopsy performed due to an elevated prostate-specific antigen (PSA)level. He complained of general malaise and had hematuria, proteinuria, and interstitial pneumonitis in the lower lung field on admission. A renal biopsy showed necrotizing crescentic glomerulonephritis. He was diagnosed as having microscopic polyangiitis (MPA) based on the presence of small-vessel vasculitis and positivity for myeloperoxidase-anti-neutrophil cytoplasmic antibody (MPO-ANCA) (465 EU). He was effectively managed with methylprednisolone pulse therapy (500 mg/day x 3 days) followed by progressive dosage tapering. In the present case, the identification of prostatic vasculitis led to the early detection of MPA, which resulted in an excellent clinical course. Prostatic involvement has been also reported in patients with Wegener's granulomatosis or Churg-Strauss syndrome. Thus, physicians should be aware of the potential for the involvement of various organs, including the prostate, in patients with ANCA-associated vasculitis.