Chronic systemic immune-mediated disorders like psoriasis, psoriatic arthritis and inflammatory bowel disease, i.e., Crohn′s disease and ulcerative colitis, affect many adults and children worldwide. Studies have indicated a possible association between inflammatory bowel disease and psoriasis and vice versa. However, whether and in which direction causal relationships exist remains unclear. 

A recent study investigated the association between inflammatory bowel disease, particularly Crohn′s disease and ulcerative colitis, and psoriasis or psoriatic arthritis.

This study utilized the summary statistics from genome-wide association studies, including up to 4,63,372 European individuals. It used inflammatory bowel disease, Crohn′s disease, ulcerative colitis, psoriasis and psoriatic arthritis as both exposures and outcomes.

The study found:

• 12,882 cases of inflammatory bowel disease and 5,621 cases of Psoriasis. The women made up 48% to 56% of the study population.
• It found an association between genetically predicted inflammatory bowel disease and a higher risk of psoriasis and psoriatic arthritis.
• Contrasting ulcerative colitis, it found an association between the Crohn′s disease subentity with psoriasis and psoriatic arthritis.
• In the reverse directions, it found no notable associations.

These findings support a causal effect between inflammatory bowel disease and psoriasis as well as psoriatic arthritis, but not vice versa. Additionally, Crohn′s disease and not ulcerative colitis seem responsible for the causal effect of inflammatory bowel disease on both psoriasis outcomes. These findings will help manage inflammatory bowel disease and psoriasis in clinical practice.

Source: Freuer D, Linseisen J, Meisinger C. Association between inflammatory bowel disease and both psoriasis and psoriatic arthritis: a bidirectional 2-sample mendelian randomization study. JAMA Dermatol. 2022 Sep 14. [Epub ahead of print]