Biogen discloses PML cases, one death in Tysabri patients

Four more patients taking Biogen Idec's multiple sclerosis drug Tysabri have developed the serious brain infection known as progressive multifocal leukoencephalopathy (PML), and one of them died, according to the company's monthly update. That brought the total number of confirmed cases as of Dec. 2 to 79, with 16 deaths. Report