TYSABRI is a prescription medicine used to treat relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease. TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML). When starting and continuing treatment with TYSABRI, it is important to discuss with your doctor whether the expected benefit of TYSABRI is enough to outweigh this risk. 

It is not known if TYSABRI is safe and effective in children under 18 years of age.