Epstein–Barr virus-associated infectious mononucleosis and risk of systemic lupus erythematosus

Objectives. Elevated levels of serological markers of EBV infection in patients with SLE and observations that infectious mononucleosis (IM) may precede some cases of SLE suggest a possible role of EBV in the aetiology of SLE. We evaluated the relationship between EBV-associated IM and subsequent risk of SLE in a population-based cohort study. Methods. We followed cohorts of Danes tested serologically for IM using the Paul–Bunnell (PB) heterophile antibody test between 1939 and 1989, and patients hospitalized with IM between 1977 and 2007 for subsequent first hospitalizations with SLE in the period 1977–2008. Standardized incidence ratios (SIRs) with 95% CI served as measures of relative risk. Results. Risk of SLE was not increased either in individuals with a positive PB test (SIR = 1.1; 95% CI 0.8, 1.6; n = 27) or in individuals hospitalized with IM (SIR = 1.3; 95% CI 0.7, 2.2; n = 12). However, SLE risk in PB-negative individuals was significantly increased (SIR = 2.6; 95% CI 2.1, 3.2; n = 82), a risk that was particularly high 1–4 years after the PB test (SIR = 6.6; 95% CI 3.3, 13.2) and remained significantly elevated for >25 years. Conclusions. EBV-associated IM does not seem to be a risk factor for SLE. The temporal pattern of increased SLE risk in individuals with a negative PB test suggests that some patients who go on to develop SLE may present with unspecific symptoms, for which they may be tested for IM, long in advance of their SLE diagnosis.