In a separate study, the overall risk of PML is reported to be 0.4/100,000 in patients with rheumatoid arthritis.  The increased risk of PML in RA patients using Rituximab is 4/100,000.  In patients with lupus, the risk of PML is higher than in RA (4/100,000) and 40% of cases of PML occur during low-dose glucocorticoid therapy without immunosuppressive therapy.

Read more about PML symptoms, diagnosis, and treatment in Progressive Multifocal Leukoencephalopathy: What is PML? Part One.

SOURCES:
NINDS Progressive Multifocal Leukoencephalopathy Information Page.  Accessed May 28, 2013.

Arkema EV, van Vollenhoven RF, et al.  Incidence of progressive multifocal leukoencephalopathy in patients with rheumatoid arthritis: a national population-based study.  Ann Rheum Dis 2012 Nov;71(11):1865-7. doi: 10.1136/annrheumdis-2012-201638. Epub 2012 Jun 27.

Carson KR, Evens AM, et al.  Progressive multifocal leukoencephalopathy after rituximab therapy in HIV-negative patients: a report of 57 cases from the Research on Adverse Drug Events and Reports project.  Blood May 2009;113(20):4834-4840. doi:10.1182/blood-2008-10-186999. Epub 2009 Mar 5.

Clifford DB, Ances B, Costello C, et al.  Rituximab-associated progressive multifocal leukoencephalopathy in rheumatoid arthritis.  Arch Neurol 2011 Sep;68(9):1156-64. doi: 10.1001/archneurol.2011.103. Epub 2011 May 9.

Fleischmann RM.  Progressive multifocal leukoencephalopathy following rituximab treatment in a patient with rheumatoid arthritis.  Arthritis Rheum 2009 Nov;60(11):3225-8. doi: 10.1002/art.24906.

Harris HE.  Progressive multifocal leucoencephalopathy in a patient with systemic lupus erythematosus treated with rituximab.  Rheumatology 2008;47(2):224-225.  doi: 10.1093/rheumatology/kem299.  Epub 2007 Nov 28.

Lach B, Connolly B, Wüthrich C, and Koralnik IJ. (2013), Inflammatory infratentorial progressive multifocal leukoencephalopathy in a patient with rheumatoid arthritis. Neuropathology. doi: 10.1111/neup.12045.

Molloy ES.  PML and rheumatology: The contribution of disease and drugs. Cleveland Clinic Journal of Medicine Nov 2011;78(Suppl 2):S28-S32. doi: 10.3949/ccjm.78.s2.07

Molloy ES, Calabrese LH.  Progressive Multifocal Leukoencephalopathy Associated With Immunosuppressive Therapy in Rheumatic Diseases: Evolving Role of Biologic Therapies.  Arthritis & Rheumatism 2012 Sep;64(9):3043-3051.  doi: 10.1002/art.34468.

Palazzo E, Yahia SA.  Progressive multifocal leukoencephalopathy in autoimmune diseases.  Joint Bone Spine 2012 Jul;79(4):351-355.  doi:10.1016/j.jbspin.2011.11.002.

Wenning W, Haghikia A, et al.  Treatment of Progressive Multifocal Leukoencephalopathy Associated with Natalizumab.  N Engl J Med 2009; 361:1075-1080. doi: 10.1056/NEJMoa0810257.

Lisa Emrich is author of the blog Brass and Ivory: Life with MS and RA and founder of the Carnival of MS Bloggers.