Severe Bilateral Optic Neuritis and a Tumefactive Demyelinating Lesion in Pregnancy.

A 40-year-old pregnant woman developed severe bilateral optic neuritis and a tumefactive demyelinating lesion (TDL) in the first trimester. Although her bilateral optic neuritis improved with intravenous methylprednisolone, plasma exchange, and intravenous immunoglobulin, the TDL lesion expanded, and the accompanying symptoms worsened. Following a shared decision-making process, the patient received ofatumumab after repeated steroid pulse therapy. Subsequently, the lesion enlargement stopped and there was no exacerbation of the symptoms. This case demonstrates the challenges and management of a rare condition involving co-occurrence of severe bilateral optic neuritis and a TDL during pregnancy.