RESUMO
Nonvasculitic autoimmune meningoencephalitis (NAIM) is a rare condition describing a syndrome of steroid-responsive encephalopathy in patients with similar clinical and pathologic features. It can be associated with autoimmune diseases, such as Sjogren's syndrome and autoimmune thyroiditis. Brain biopsies usually show inflammatory cells without evidence of vasculitis. In this article, we present a patient who developed NAIM after receiving rituximab, a B-cell-depleting therapy for rheumatoid arthritis. The brain biopsy showed a lack of B lymphocytes in the brain tissue, and the patient responded well to intravenous immunoglobulins. We further discuss the role of B lymphocytes and specific regulatory B lymphocytes in suppressing autoimmunity in the brain and propose that the depletion of regulatory B cells may contribute to the pathogenesis of NAIM. This case illustrates a potential side effect of rituximab and demonstrates the importance of regulatory B cells in maintaining the immune response.