Multifocal neurological involvement as the only manifestation of IgG4-related disease.

A 46-year-old man with progressive visual loss underwent brain MRI showing multifocal nodular pachymeningeal thickening involving optic nerve meninges bilaterally and internal acoustic meatus dura mater (Figure 1). Diffuse meningiomatosis was diagnosed and radiation therapy was given with symptom stabilization. Four years later left hearing loss and right hypoacusia occurred, with slight transient improvement after high-dose dexamethasone. Serum IgG4 was increased. CSF analysis showed increased protein, oligoclonal IgG, plasma cells, and lymphocytes. Cerebral biopsy showed meningeal plasma-cell granuloma with IgG4- positive polyclonal plasma-cells and B-lymphocyte infiltration (Figure 2). IgG4- Related-Disease was diagnosed.1 Rituximab was unsuccessful. IgG4-Related-Disease is a fibroinflammatory multi-organ condition characterized by tumefactive lesions and lymphoplasmacytic infiltrates rich in IgG4-positive plasma-cells that may affect every organ; serum IgG4 may be elevated. Although IgG4-Related-Disease with exclusive multifocal central nervous system localization is extremely rare and often misdiagnosed,2-4 it should be considered in the differential diagnosis of tumor-like intracranial lesions and hyperthrophic pachymeningitis.