Knowledge around risk factors for progressive multifocal leukoencephalopathy (PML) in HIV-infected patients in the era of antiretroviral therapy (ART) is limited. The authors studied HIV-1-infected patients aged ≥15 years who had no history of PML and were prospectively followed up between 1997 and 2011. They found that PML developed in 555 patients, and in 57 of whom it developed during the first 6 months of ART. From 1997-2000 to 2009-2011, the incidence fell from 1.15 to 0.49 per 1000 person-years. Compared with men who have sex with men, the authors found that injection drug users (IDUs) were at higher risk (HR 1.80, 95%CI 1.32-2.45 for male and 1.68, 95%CI 1.13-2.48 for female IDUs). When IDUs were excluded, hepatitis C virus seropositivity was also associated with an increased risk (HR 1.40, 95%CI 1.02-1.93). Compared with no ART initiation, initiation <6 months previously was associated with PML onset (HR 4.91, 95%CI 2.42-9.95). Therefore recent ART initiation, injection drug use and hepatitis C virus seropositivity is associated with an increased risk of PML.
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