A 74-year-old male was referred for the sudden onset of bilateral sudden deafness. The patient had no history of any disease or trauma to the head. Pure tone audiometry revealed bilateral moderate, to severe, sensorineural hearing loss. Auditory brain stem responses (ABRs) showed normal peak and interpeak latencies. These audiological findings suggested that his hearing loss could be attributed to inner ear lesions. However, we felt an alternative explanation for this sudden deafness was likely to exist because the patient also had a month-long fever of unknown origin (FUO) and weight loss of 5 kg/month. Using the criteria of The American College of Rheumatology, we made the diagnosis of polyarteritis nodosa (PAN). Serum MPO-ANCA was positive (× 661).

For treatment, the patient was begun on prednisolone and cyclophosphamide. Nine months later, fever, hypertension, nephritis, pneumonitis, and arthritis had completely resolved, the MPO-ANCA became negative (MPO-ANCA < × 10). Furthermore, his hearing improved.