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

Summary 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.