Progressive multifocal leukoencephalopathy and reversible progressive leukoencephalopathy syndrome in dermatologic therapy.

Progressive multifocal leukoencephalopathy (PML) is a frequently fatal demyelinating disease of the brain caused by activation of the John Cunningham virus. It typically occurs in immunocompromised patients, including transplant recipients on immunosuppressant medications, patients receiving chemotherapy for hematologic malignancies, and patients with human immunodeficiency virus. Unfortunately, there is no effective treatment for PML. By contrast, reversible progressive leukoencephalopathy syndrome (RPLS) is a generally treatable disorder that is diagnosed based on clinical symptoms (eg, altered mental status, visual abnormalities, headache, and seizures) and neuroradiographic changes (eg, cerebral edema). It is classically associated with malignant hypertension and immunosuppressive medications. Symptoms usually resolve over time, or with treatment of the underlying cause. Amid the relatively recent withdrawal of efalizumab from the US market because of its association with PML, and the added warning found on ustekinumab describing RPLS as a possible adverse effect, there has been an increasing level of concern in dermatology that biologics and other systemic medications used in the treatment of psoriasis may be related to an increased risk of specific leukoencephalopathies. In this review, we evaluate the association of prebiologics (eg, cyclosporine, methotrexate, acitretin) and biologics (eg, adalimumab, alefacept, efalizumab, etanercept, infliximab, rituximab, and ustekinumab) with the potential risk of developing PML and RPLS.