Granulomatosis with polyangiitis initially presenting as frequent urination mimicking a prostatic abscess: A case report.

Granulomatosis with polyangiitis (GPA) rarely involves the urological system. Herein, we report the case of a 71-year-old man with GPA who presented with frequent urination and a computed tomography detected low-density area in the enlarged prostate, suggesting an abscess. The initial prostate biopsy revealed necrotic tissue consistent with a prostate abscess, with severe destruction ultimately leading to a bladder fistula. However, upon further review of the pathology samples, multinucleated giant cells were identified, raising suspicion for GPA. Further history revealed bloody nasal discharge, and biopsy results from a lung mass also indicated GPA. Based on these findings-along with sinusitis and proteinase-3-anti-neutrophil cytoplasmic antibody positivity-the diagnosis of GPA was made. Our patient was treated with steroid pulse therapy; however, disease progression could not be controlled, and he died suddenly due to haemorrhagic cerebral infarction. Autopsy revealed granulomas in the lungs and spleen, crescentic glomerulonephritis in the kidneys, and haemorrhagic infarction with an embolised fibrin clot in the brain. Urogenital lesions in GPA can be challenging to diagnose due to their nonspecific presentation, and clinicians should consider GPA in patients presenting with unexplained prostatitis and systemic symptoms, as early diagnosis and treatment could prevent unnecessary surgeries and improve prognosis.