Introduction: IgG4RD, a recently described entity affecting multiple organs/sites, is typically characterized by tumefactive lesions, fibrosis, lymphoplasmacytic infiltrate and possible elevated serum IgG4. Clinically, IgG4RD may mimic malignancy or inflammatory processes but histopathology is often non-specific. The disease usually responds to long-term glucocorticosteroid and immunosuppressant therapy. We present the first skull base case series of IgG4RD from the United States.

Methods: A retrospective review of skull base IgG4RD cases at our institution was conducted through the Departments of Neurosurgery and Otorhinolaryngology.

Results: Presentation in our IgG4RD patients was initially suspicious for malignancy or invasive infection. Clinical suspicion and repeat pathology review were critical in establishing IgG4RD diagnosis. Patient #1 presented after multiple non-diagnostic biopsies for cervical lymphadenopathy. MRI for recent retro-orbital pain showed a unilateral enhancing cavernous sinus mass (Figure G). Review of previous pancreatectomy histopathology revealed IgG4RD (known cause of auto-immune pancreatitis). Review of prior lymph nodes biopsies also confirmed IgG4RD. Patient #2 (Figures A and B) presented with fever, headache, diabetes and an enhancing, infiltrative petroclival mass. Osteomyelitis was initially suspected on biopsy. Repeat pathology review showed polyclonal plasmacytosis with increased IgG4-positive plasma cells (Figures E and F). Patient #3 presented with massive destructive of the nasal septum and ethmoid sinuses with extension to the anterior subfrontal skull base(Figures C and D). Lymphoma and vasculitis were suspected. Biopsies showed only inflammation and fibrosis. Repeat review and staining revealed increased IgG4-positive plasma cells.

Conclusions: Once corticosteroid/ immunosuppressant therapy was initiated for IgG4RD, all patients showed clinical improvement. Skull base IgG4RD may be under-recognized. A high index of suspicion is required to expedite diagnosis, minimize morbidity from multiple biopsies and initiate treatment.

Patient Care: IgG4RD involving the skull base may be more prevalent than we think. This presentation will improve patient care by describing the signs and symptoms of this under-recognized disease process allowing physicians to be aware of this clinico-pathological entity.

Learning Objectives: At the conclusion of this presentation, the participants should be able to recognize the salient features of IgG4-related skull base disease, and also become familiar with its diverse clinical presentation, diagnostic tools and treatment.

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