RT Journal Article SR Electronic T1 PML and rheumatology: The contribution of disease and drugs JF Cleveland Clinic Journal of Medicine JO Cleve Clin J Med FD Cleveland Clinic SP S28 OP S32 DO 10.3949/ccjm.78.s2.07 VO 78 IS 11 suppl 2 A1 Molloy, Eamonn S. YR 2011 UL http://www.ccjm.org/content/78/11_suppl_2/S28.abstract AB Progressive multifocal leukoencephalopathy (PML), a rare, typically fatal, opportunistic infection caused by the JC virus, is becoming relevant to physicians in multiple specialties, including those who prescribe biologic agents for the treatment of autoimmune disorders. Reports of PML have led to US Food and Drug Administration alerts and warning letters regarding four immunosuppressive agents in recent years (natalizumab, rituximab, efalizumab, and mycophenolate mofetil). Consequently, informed clinical decision-making requires understanding the risk of PML associated with these therapies. An estimate of the relative frequency of PML associated with specific rheumatic conditions has been generated. Systemic lupus erythematosus appears to be associated with susceptibility to PML that cannot be fully explained by the intensity of immunosuppressive therapy. Further, the use of rituximab in patients with rheumatic disease has raised concerns. However, definitive attribution of cause is precluded by the limitations of the currently available data. All patients with rheumatic disease, regardless of the intensity of their current immunosuppressive therapy, should be considered potentially at risk of PML. With an evolving understanding of a greater clinical heterogeneity of PML, advances in diagnostic methods, and significant implications for therapy, PML should be considered in the differential diagnosis of neurologic manifestations of rheumatic diseases.