Cytomegalovirus Encephalitis Under Fingolimod Mimicking Progressive Multifocal Leukoencephalopathy

Fingolimod, a sphingosine-1-phosphate receptor modulator approved for the treatment of relapsing multiple sclerosis (RMS), may rarely lead to CNS infections through reactivation of herpesviruses or JC virus (JCV), the cause of progressive multifocal leukoencephalopathy (PML).1,2 The authors present a patient with clinical and MRI features suggestive of PML under fingolimod. Repeat PCR testing for JCV DNA in CSF was negative, whereas cytomegalovirus (CMV) DNA was found positive. Treatment with ganciclovir was followed by clinical and MRI improvement. A 37-year-old man was diagnosed with clinically isolated syndrome after developing cervical myelitis with MRI showing few supratentorial lesions and CSF positive for oligoclonal bands. He subsequently converted to RMS with recurrent relapses of spinal symptoms. After 4 years of treatment with interferon-beta 1b, he was switched to …