Giant skull base mass need not be a tumor - a rare presentation of IgG4-related disease

Giant intracranial 'IgG4-related' lesions are uncommon. They may present as pachymeningitis or localized mass. Here we report, probably, the largest IgG4 skull base mass ever to be reported.

A 40-year male presented with headache, diplopia, right-sided sensori-neuronal hearing loss, and left spastic hemiparesis. Magnetic resonance imaging showed a lesion of 8.5 cm extending from the paranasal sinuses to the right petroclival region with uniform contrast enhancement and T2 hypointensity. Endonasal biopsy revealed respiratory epithelium with fibrosis, and lymphoplasmacytic infiltrate having IgG4 positive cells >30/HPF suggestive of 'IgG4-related' disease. Serum IgG4 was within normal levels. With oral prednisolone 60 mg given daily for 6 weeks and then tapered off over 8 weeks, he improved symptomatically.

Though rare, 'IgG4-related' disease can also present as a giant skull base mass and should be kept as a differential to fungal granulomas and meningiomas. As they improve dramatically with medical management, extensive skull base resection should not be planned before obtaining a tissue biopsy, especially when there is extension into paranasal sinuses and T2 hypointensity.