A Case of Primary Central Nervous System Lymphoma That Developed in a Patient Receiving Fingolimod Therapy for Multiple Sclerosis.

Fingolimod is an oral medication for the prevention of multiple sclerosis relapse, and its efficacy has been demonstrated in several clinical trials. Fingolimod has various side effects, such as arrhythmia and hepatic dysfunction. In addition, there have been rare reports of the development of lymphoproliferative disorders in patients undergoing fingolimod therapy, including primary central nervous system lymphoma (PCNSL).