Inflammatory bowel disease may cause psoriasis, psoriatic arthritis

Inflammatory bowel disease appears to be a causal risk factor for both psoriasis and psoriatic arthritis, with Crohn’s disease specifically associated with the development of the two psoriasis outcomes, according to a study.

Researchers performed a bidirectional two-sample Mendelian randomization study, with summary statistics obtained from genome-wide association studies that involved a total of 463,372 European individuals. They estimated total and direct effects by conducting an iterative radial and robust inverse-variance weighted method.

In the cohort, 12,882 individuals had inflammatory bowel disease and 5,621 had psoriasis. The proportion of women ranged from 48 percent to 56 percent.

Pooled data indicated that genetically predicted inflammatory bowel disease was linked to a heightened risk of psoriasis (pooled odds ratio [OR], 1.10, 95 percent confidence interval [CI], 1.05–1.15; p<0.001) and psoriatic arthritis (pooled OR, 1.10, 95 percent CI, 1.04–1.18; p=0.003).

Of note, the causal effect of inflammatory bowel disease on psoriasis outcomes was driven by Crohn’s disease (psoriasis: OR, 1.16, 95 percent CI, 1.12–1.20; p<0.001; psoriatic arthritis: OR, 1.13, 95 percent CI, 1.06–1.20; p<0.001) but not ulcerative colitis.

Meanwhile, psoriasis and psoriatic arthritis had no causal effect on inflammatory bowel disease.

The present data may have important implications, especially for the management of inflammatory bowel disease and psoriasis in clinical practice.