Characteristics and antecedents of progressive multifocal leukoencephalopathy in an insured population.

Based on health insurance claims from a large U.S. health insurer, the authors identified 44 progressive multifocal leukoencephalopathy (PML) cases from 2002 through 2004 and described their characteristics, including antecedent diagnoses and treatments as well as survival. Immunosuppressive conditions such as HIV/AIDS, rather than potentially immunosuppressive treatments, were the main antecedents of PML. A lower mortality was observed among PML patients whose antecedent diagnosis was HIV/AIDS, the majority of whom received highly active antiretroviral therapy.