Progressive multifocal leukoencephalopathy (John Cunningham virus)

Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of the John Cunningham virus (JCV). PML is a serious adverse effect of natalizumab treatment for relapsing-remitting multiple sclerosis. It can also occur in advanced HIV infection and as a rare adverse effect of immunosuppressive therapy and cancer chemotherapy.

In patients taking natalizumab, the estimated incidence of PML is 2.1 cases per 1000 patients treated. Assess the patient’s risk of PML before starting natalizumab. Consult the product information for pretreatment screening and risk assessment criteria.

Monitor patients receiving natalizumab for features of PML such as progressive cognitive decline, visual changes, ataxia and seizures.