Granulomatosis with polyangiitis affecting the skull base and manifesting as spontaneous skull base osteomyelitis

A 53-year-old woman presented with right-sided otalgia radiating to the temporal region, angle of the mandible and upper neck. Otoscopy was unremarkable on examination and there were no signs of otitis externa. MRI revealed an infiltrative soft tissue mass to the right lateral aspect of the clivus. Transnasal and CT-guided biopsies were performed, however, these showed either inconclusive or benign tissue. Following multidisciplinary team assessment a diagnosis of spontaneous skull base osteomyelitis was made and treatment with intravenous antibiotics started. Failure to respond to antimicrobials and the development of cranial nerve palsies raised the possibility of a vasculitis. Subsequently, a clinical diagnosis of granulomatosis with polyangiitis (GPA) was made. Remission has now been maintained with cyclophosphamide and prednisolone. We discuss the rare presentation of GPA mimicking that of spontaneous skull base osteomyelitis as well as its management and related primary otolaryngological manifestations.