Immunoglobulin G4-Related Disease Presenting as Temporal Bone Lesion with Facial Nerve Palsy

Immunoglobulin G4-related disease (IgG4-RD) is a systemic condition which could present as local infiltration of skull base structures. We report a case of IgG4-RD with infiltration of the temporal bone and surrounding structures in a patient with systemic vasculitis on systemic steroids. A 31-year-old woman presented with right-sided facial weakness, headache, and right ear hearing loss. On examination, redness and retraction of the right tympanic membrane and facial paresis (House-Brackman IV) were noted. Computed tomography imaging showed mastoiditis, temporal lobe stroke, and brain abscess. Magnetic resonance imaging (MRI) showed infiltration in the infratemporal fossa, nasopharynx, spreading along the Eustachian tube and perineurally along the branches of CN V and CN VII intracranially, forming a dural based mass in the middle cranial fossa. Intracranial mass compressed the temporal lobe of the brain, causing perifocal brain edema. Endoscopic biopsy of the nasopharynx was chosen as the least invasive method. It showed marked fibrosis of the tissue, dense lymphoplasmacytic infiltrates, and an increased number of IGG4-positive plasma cells. Serum IgG4 levels were below the diagnostic criteria of IgG4-RD, but histological characteristics of IgG4-RD were met. The patient was treated with high-dose oral prednisolone. Resolution of symptoms, including facial nerve paresis, was observed and infiltration in the nasopharynx, infratemporal fossa decreased on subsequent MRI tests. No recurrence was noted on the follow-up of 16 months. The case presented itself as a diagnostic challenge for a multidisciplinary team to differentiate pathology caused by either IgG4-RD, systemic vasculitis, or atypic mastoiditis. MRI and histological reports were essential to establish a correct diagnosis.