Hemorrhagic cystitis complicating untreated necrotizing vasculitis.

Although the genitourinary system is frequently affected in polyarteritis nodosa, involvement of the wall of the urinary bladder is extremely uncommon; moreover, when reported, it has been merely as an incidental finding late in the disease course. In contrast, hemorrhagic cystitis is a well-recognized complication of cyclophosphamide therapy for the systemic vasculitides, but has not previously been reported to complicate untreated vasculitis. Herein is described a patient who presented with non-treatment-related hemorrhagic cystitis which was found to be due to nongranulomatous necrotizing vasculitis of the wall of the urinary bladder. This represents both a novel presentation of polyarteritis and a previously unreported etiology of hemorrhagic cystitis. The differential diagnosis of apparently spontaneous hemorrhagic cystitis should therefore include active necrotizing vasculitis, independent of prior therapy.