[Progressive multifocal leukoencephalopathy as a complication of natalizumab therapy].

Natalizumab medication used in the treatment of active relapsing-remitting multiple sclerosis is associated with a risk of contracting progressive multifocal leukoencephalopathy (PML). Current risk of the PML disease in connection with natalizumab therapy in multiple sclerosis patients is 2.77/1,000. By December 2012, more than 108,000 multiple sclerosis patients worldwide have received natalizumab therapy. There are 350 multiple sclerosis patients receiving natalizumab in Finland. We describe the first one of the two Finnish multiple sclerosis patients having so far been diagnosed with PML disease as a complication of natalizumab therapy.