Severe coxsackie virus B5 encephalitis mimics autoimmune limbic encephalitis in a young woman under long-term B-cell depletion with ocrelizumab: A case report.

Summary: A young woman receiving long-term treatment with ocrelizumab for Multiple Sclerosis faced a life-threatening medical mystery. Ocrelizumab works by depleting B-cells to control MS, but this also weakens the body's defense against certain infections. She developed severe brain inflammation (limbic encephalitis) that doctors initially mistook for an autoimmune flare-up. Consequently, they suppressed her immune system further, which caused her condition to worsen. Eventually, the true culprit was identified: a Coxsackie B5 virus infection. Doctors switched strategies, treating her with antiviral medications (ribavirin and favipiravir) and intravenous immunoglobulins (IVIG). After four weeks, her condition stabilized, though she was left with lasting memory and cognitive difficulties. This case highlights how common viruses can mimic autoimmune attacks in patients on immune-suppressing drugs.