Natalizumab-associated reversible encephalopathy syndrome mimicking progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy is a rare but potentially lethal adverse event in natalizumab treated multiple sclerosis patients. We report on a 40-year old Caucasian man with typical relapsing progressive multiple sclerosis, who developed a reversible leukoencephalopathy syndrome after 43 natalizumab infusions mimicking progressive multifocal leukoencephalopathy. To our knowledge, this is the first case of its kind. Our case suggests that awareness ought to be sharpened for reversible leukoencephalopathy syndrome in the follow-up of natalizumab treated multiple sclerosis patients.