Reactivation Of Herpesvirus Under Fingolimod: A Case Of Severe Herpes Simplex Encephalitis

Fingolimod (FTY720, Gilenya, Novartis Pharma AG, Basel, Switzerland) is a sphingosin-1-phosphate (S1P) receptor modulator with immunomodulatory properties that traps naive and central memory T cells in lymph nodes, leading to reduced numbers of peripheral blood lymphocytes, and is the first licensed oral drug for multiple sclerosis (MS).(1,2) We report a case of a near fatal herpes simplex virus 1 (HSV-1) encephalitis under the licensed dose of fingolimod in a patient with MS.