Progressive Multifocal Leukoencephalopathy after Natalizumab Therapy for Crohn's Disease

In a man with Crohn's disease who was treated with natalizumab and subsequently died, reexamination showed that the fatal lesion was progressive multifocal leukoencephalopathy and not an astrocytoma. Analysis of serial serum specimens showed that JC virus first appeared about three months after the initiation of natalizumab therapy. In a man with Crohn's disease who was treated with natalizumab and subsequently died, reexamination showed that the fatal lesion was progressive multifocal leukoencephalopathy. Natalizumab has great therapeutic potential in both multiple sclerosis and inflammatory bowel disease. 1 – 3 Two cases of progressive multifocal leukoencephalopathy (PML) have recently been reported in patients with multiple sclerosis who were treated with a humanized monoclonal antibody against α 4 integrins, natalizumab (Tysabri, Elan and Biogen Idec), in combination with interferon beta-1a (Avonex, Biogen Idec). 4 One of these cases is described elsewhere in this issue of the Journal . 5 We report a third case of PML — this one in a patient with Crohn's disease who received 300 mg of open-label natalizumab intravenously every four weeks as part of . . .