Severe aseptic temporal lobe encephalitis on fingolimod

We report the case of an MS patient with aseptic temporal lobe encephalitis while on treatment with fingolimod. This 49-year-old woman developed headache and decreasing level of consciousness after 3.5 years of fingolimod therapy. Imaging, CSF studies, and rapid clinical response to acyclovir suggested a viral etiology, although CSF cultures and viral PCR were negative. This case illustrates the potential for severe manifestations of infectious illnesses on fingolimod, which may have a predilection for the CNS and also include herpes virus infections, cryptococcus, and PML. Efforts to prevent these secondary infections are limited by a lack of established risk factors.