An Adult Case of Severe, Refractory, and Progressive Leukodystrophy‐Like Diffuse Encephalitis With <scp>MOG</scp> ‐ <scp>IgG</scp> Treated With Rituximab

ABSTRACT Background Myelin oligodendrocyte glycoprotein (MOG) antibody‐associated disease (MOGAD) is typically considered responsive to immunotherapy with a good prognosis. However, some patients develop severe symptoms and the underlying pathologic and immunologic mechanisms remain unclear. We report a severe, progressive, and fatal case of MOGAD treated with rituximab (RTX). Case Presentation A 43‐year‐old woman was admitted to the hospital for bilateral vision loss followed by a convulsive seizure and comatose state. Her serum and cerebrospinal fluid (CSF) tested positive for MOG‐IgG using our in‐house living cell–based assay, with higher antibody titers in her CSF than in her serum. She was diagnosed with MOGAD and treated with intravenous methylprednisolone, plasma exchange therapy, and immunoglobulin therapy. However, she was refractory to these treatments, leading to progressive leukodystrophy‐like white matter lesions. A brain biopsy at this time revealed widespread demyelination as well as massive infiltration of CD4‐positive cells and macrophages. We then treated her with intravenous cyclophosphamide therapy. Still, her MRI showed progressive exacerbation, and we detected a marked increase in B‐cell lineage cells such as CD19 + CD27 − IgD − CXCR5 − (double‐negative B cells) and plasma cells in peripheral blood and CSF. As a result, we tried RTX, which resulted in MRI lesion reduction in part initially after a progressively worsened course. The comatose state persisted, and she eventually died of aspiration pneumonia 1 year later. Conclusions We report a severe refractory case of MOGAD that responded only to RTX. Early RTX treatment should be considered for patients with severe MOGAD.