Inflammatory bowel disease associated with chronic inflammatory skin diseases

A new study revealed that inflammatory bowel disease was associated with various chronic inflammatory skin diseases. IBD incidence was increased in patients with hidradenitis suppurativa, and CD was increased in patients with psoriasis. The study results were published in the journal British Journal of Dermatology.  

Several studies done in the past have linked various chronic inflammatory skin diseases (CISDs) with inflammatory bowel disease (IBD). But there are mixed conclusions hence researchers conducted a study to compare the incidence of IBD – ulcerative colitis (UC) and Crohn's disease (CD) – in patients with a CISD vs. similar persons without a CISD. 

Using nationwide, longitudinal, commercial insurance claims data from the USA, a cohort study was done on adults and children between 2004 and 2020 diagnosed with either psoriasis, atopic dermatitis, alopecia areata, vitiligo, or hidradenitis suppurativa. Comparator patients were identified through risk-set sampling. They were considered eligible if they were seen by a dermatologist at least twice and not diagnosed with a CISD. Patient follow-up was done until either IBD diagnosis, death, disenrollment, or end of the data stream, whichever came first. IBD events, UC or CD, were identified via validated algorithms using hospitalization or diagnosis with endoscopic confirmation. Incidence rates were computed before and after adjustment via propensity-score decile stratification to account for IBD risk factors. Hazard ratios (HR) and 95% confidence intervals (CIs) were estimated to compare the incidence of IBD in CISD vs. non-CISD. 

Results: 

• There were 123 614 patients with atopic dermatitis,83 049 patients with psoriasis, 18 135 patients with alopecia areata, 9003 patients with vitiligo or 6806 patients with hidradenitis suppurativa, and 2 376 120 comparator patients without a CISD.
• An increased risk of both UC and CD in patients with hidradenitis suppurativa, an increased risk of CD but not UC in psoriasis, and no increased risk of IBD in atopic dermatitis, alopecia areata, or vitiligo was seen during a median follow-up time of 718 days, and after applying propensity-score adjustment for IBD risk factors. 

Take-home points: 

• By providing background rates for IBD across multiple CISDs using consistent methods and within a single, nationally representative patient population, this large-scale, claims-based cohort study expands current knowledge.
• A relatively increased risk of IBD was observed in patients with hidradenitis suppurativa, but the overall incidence rate difference of IBD was generally low.
• Patients with psoriasis had an increased risk of Crohn's disease only, but patients with atopic dermatitis, vitiligo, or alopecia areata did not have an increased risk of either Crohn's disease or ulcerative colitis.

Further reading: Schneeweiss MC, Kirchgesner J, Wyss R, et al. Occurrence of inflammatory bowel disease in patients with chronic inflammatory skin diseases: a cohort study. Br J Dermatol. 2022;187(5):692-703. doi:10.1111/bjd.21704