Diagnostic Quandary of Granulomatosis With Polyangiitis Presenting First in the Petrous Apex

Objectives: To describe a rare case of granulomatosis with polyangiitis (GPA) initially presenting at the petrous apex, accompanied by a brief literature review. Methods: A detailed retrospective single-case study of a 29-year-old male diagnosed with GPA. A review of the scientific literature of GPA affecting the petrous apex, causing cranial neuropathies and/or ottorhrea was conducted. Results: A 29-year-old male with a history of schizophrenia presented with right-sided otalgia, initially diagnosed as acute otitis media. Despite antibiotics, his symptoms persisted. Weeks later, he returned with cranial neuropathies and clear otorrhea. Imaging findings lead to a working diagnosis of skull base osteomyelitis despite noninfectious signs. His course was further complicated by his discharge against medical advice. Eventually, he was found to have a septal perforation and diffuse nasal inflammation. An autoimmune workup revealed c-ANCA-positive GPA. Subsequent kidney biopsy confirmed GPA, and appropriate therapy led to clinical improvement and near-complete resolution of skull base inflammation. Conclusions: This case underscores the diagnostic complexity of GPA. Initial misdiagnosis of infection delayed appropriate treatment. Awareness of the varied presentations of GPA, including rare manifestations like skull base involvement and symptoms such as otorrhea and conductive hearing loss, is valuable. Early consideration of autoimmune etiologies and timely serological and histopathological analyses can prevent diagnostic delays and unnecessary treatments, improving patient outcomes.