Anti-MPO small-vessel vasculitis causing prostatis and nephritis.

Microscopic polyangiitis is a necrotizing angiitis involving capillaries, venules, and arterioles. The vascular beds of various organs may be involved, causing varying presentations. To our knowledge, this is the first case of anti-myeloperoxidase (anti-MPO) antibody small-vessel vasculitis causing prostatic vasculitis. A 79 year-old nonsmoker American man presented with symptoms of fevers, malaise, weight loss, and cough. Urine analysis revealed hematuria. Blood tests were remarkable for an elevated prostate-specific antigen (PSA) and a serum creatinine of 3.1 mg/dl (baseline, 1.2 mg/dl). Computed tomography (CT) scan of the thorax revealed a 4.7-cm mass in the left lower lobe of the lung. Metastatic prostate cancer was suspected. Therefore, prostatic biopsy was performed. The biopsy revealed fibrinoid degeneration with vasculitic changes involving the arterioles. When evaluated by nephrology, his serum creatinine was 9.9 mg/dl. A renal biopsy was performed, which revealed focal segmental necrotizing glomerulopathy with microscopic vasculitis. All the serologies were normal, with the exception of low C4, and positive perinuclear antineutrophil cytoplasmic antibodies (ANCA) associated with anti-MPO. The patient was started on intermittent hemodialysis, steroids, and oral cytoxan. Despite treatment, with improvement of the respiratory and constitutional symptoms, the patient remained dialysis-dependent. He later decided to discontinue dialysis and subsequently expired. Vasculitic involvement of the prostate is an uncommon manifestation of microscopic polyangiitis. This bedazzling entity is challenging to diagnose and thus makes it difficult to treat in a timely manner.