Background/Purpose:

Patients with systemic lupus erythematosus (SLE) are at increased risk of developing coronary heart disease as well as infections. Acute infections have been recognized to be associated with the development of arterial coronary events and previous studies have also demonstrated an increased risk of deep venous thrombosis and pulmonary embolism following an infection in general population.  Our aim was to determine if there is an association between infections and risk of arterial and venous thrombotic events in patients with SLE.

Methods:

Based on both retrospectively and prospectively collected data on 571 adult SLE patients fulfilling the ACR classification criteria, we identified all cases of acute infections requiring hospitalization, cutaneous herpes zoster, as well as arterial and venous thrombotic events. For each patient, the start of follow-up was the date of SLE diagnosis, and the end of follow-up was date of death or most recent information recorded.

Patients were divided into 3 groups based on infection type: respiratory, cutaneous herpes zoster and other (urinary tract, cerebral, gastrointestinal, gynecological, cutaneous infections, bacteremia and bacterial endocarditis). Period of interest (POI) was defined as one year following an infection. Poisson regression analysis was used to estimate relative risks (RR) and their 95% confidence intervals (CI).

Results :

Of the 571 enrolled patients 89% were female and the mean age at diagnosis was 36 ±  16 years. The mean length of follow-up was 8.9 ± 7.6 years. The total amount of patient years of follow-up was 4925 years.  271 infections (104 acute respiratory, 41 cutaneous herpes zoster and 126 other acute infections), as well as 98 arterial and 61 venous thromboses were identified.  The table presents number of infections, number of thromboses during and outside POI, RR and corresponding 95% CI for arterial and venous thromboses in patients with different infection types.

Table 1. Association between infections and thrombotic events in SLE patients

Conclusion:

Our data showed that SLE patients were at increased risk of developing an arterial thrombosis within 12 months following a respiratory infection, and similar risk was observed for cutaneous herpes zoster and other infections. For venous thrombosis, the risk was increased following respiratory infections, but not following cutaneous herpes zoster or other infections. These data suggest that the increased risk of thromboses observed in SLE patients may also be partly explained by infections. To our knowledge, this is the first study describing an association between infections and risk of thromboses in SLE patients.