Incidence of benign upper respiratory tract infections, HSV and HPV cutaneous infections in inflammatory bowel disease patients treated with azathioprine

Aliment Pharmacol Ther. 2009 May 15;29(10):1106-13. doi: 10.1111/j.1365-2036.2009.03973.x. Epub 2009 Feb 15.


Background: There are few data on the incidence of benign infections (upper respiratory tract infections, herpes lesions and viral warts) during exposure to azathioprine.

Aims: To determine the incidence of benign infections in IBD out-patients receiving azathioprine (AZA+) and to look at the influence of leucocyte counts in the onset of these events.

Methods: A total of 230 patients were included in a prospective cohort and observed during 207 patient-years. Episodes of benign infections were collected and incidences of benign infections were compared between the AZA+ group and patients without AZA (AZA-).

Results: The incidence of upper respiratory tract infections in the cohort was 2.1 +/- 2.2 per observation-year. There was no difference between the AZA+ (n = 169) and AZA- (n = 61) groups (2.2 +/- 2.3 vs. 2.1 +/- 2.1, P = 0.77). The incidence of herpes flares was significantly increased in the AZA+ group compared to the AZA- group (1.0 +/- 2.6 vs. 0.2 +/- 0.8 per year, P = 0.04). Similarly, there were significantly more patients with appearance or worsening viral warts in the AZA+ group (17.2% (AZA+) vs. 3.3% (AZA-), P = 0.004).

Conclusion: This study suggests that the incidence of herpes flares and the appearance or worsening of viral warts are increased in IBD patients receiving AZA.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Azathioprine / adverse effects*
  • Cohort Studies
  • Female
  • Herpes Simplex / pathology
  • Humans
  • Immunosuppressive Agents / adverse effects*
  • Inflammatory Bowel Diseases / drug therapy*
  • Male
  • Middle Aged
  • Papillomavirus Infections / chemically induced*
  • Prospective Studies
  • Respiratory Tract Infections / chemically induced*
  • Young Adult


  • Immunosuppressive Agents
  • Azathioprine