title: Incidence and risk factors for progressive multifocal leukoencephalopathy among patients with selected rheumatic diseases.
abstract: OBJECTIVE
  To ascertain the incidence of progressive multifocal leukoencephalopathy (PML) in patients with selected rheumatic diseases, to describe the characteristics of PML cases occurring in this setting, and to evaluate the extent to which such cases occurred in the context of biologic therapies such as rituximab or tumor necrosis factor antagonists.
  
  
  METHODS
  We conducted a large population-based study to describe the incidence and risk factors for PML among patients with rheumatoid arthritis, psoriatic arthritis, psoriasis, juvenile idiopathic arthritis, inflammatory bowel disease, and ankylosing spondylitis using national inpatient and outpatient administrative data from the entire Center for Medicare and Medicaid Services from 2000-2009. Suspected PML cases were identified using hospital discharge diagnosis codes. Risk factors for PML were evaluated using outpatient data ≥6 months prior to PML diagnosis.
  
  
  RESULTS
  Among 2,030,578 patients with autoimmune diseases of interest, a total of 53 PML cases were identified (2.6 per 100,000 patients). Most PML cases had human immunodeficiency virus (HIV) and/or cancer. Nine PML cases had evidence for biologic use prior to PML hospitalization, of which 3 had neither HIV nor malignancy and were exposed to biologics within 12 (rituximab) or 6 months (all other biologics) prior to PML diagnosis. PML occurred at an estimated incidence of 0.2 per 100,000 patients with autoimmune diseases who did not have HIV or malignancy.
  
  
  CONCLUSIONS
  PML occurs at a very low incidence among patients with rheumatic diseases but can occur even in the absence of HIV or malignancy.
authors.affiliation: University of Alabama at Birmingham, AL, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bharat
authors.forename: F
authors.initials: F
authors.lastname: Xie
authors.forename: J W
authors.initials: JW
authors.lastname: Baddley
authors.forename: T
authors.initials: T
authors.lastname: Beukelman
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.forename: L
authors.initials: L
authors.lastname: Calabrese
authors.forename: E
authors.initials: E
authors.lastname: Delzell
authors.forename: C G
authors.initials: CG
authors.lastname: Grijalva
authors.forename: N M
authors.initials: NM
authors.lastname: Patkar
authors.forename: K
authors.initials: K
authors.lastname: Saag
authors.forename: K L
authors.initials: KL
authors.lastname: Winthrop
authors.forename: J R
authors.initials: JR
authors.lastname: Curtis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058846:Antibodies, Monoclonal, Murine-Derived / Q000627:therapeutic use; D006801:Humans; D015994:Incidence; D007968:Leukoencephalopathy, Progressive Multifocal / Q000453:epidemiology*; D012189:Retrospective Studies; D012216:Rheumatic Diseases / Q000150:complications* / Q000188:drug therapy; D012307:Risk Factors; D000069283:Rituximab; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors; D014481:United States / Q000453:epidemiology
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D014409:Tumor Necrosis Factor-alpha; D000069283:Rituximab