Inflammatory bowel disease (IBD) appears to have a causal impact on psoriasis, especially psoriatic arthritis (PsA), and total psoriasis and PsA are associated with Crohn disease (CD), according to a study recently published in the Frontiers of Immunology .

Yajia Li, from Central South University in Changsha, China, and colleagues used a mendelian randomization (MR) approach to examine whether there is a causal relationship between IBD and psoriasis. A two-sample MR was conducted with the genetic instruments identified for IBD and its main subtypes, CD and ulcerative colitis (UC), using data from a genome-wide association study (GWAS) with 25,042 IBD cases and 34,915 controls. Summarized psoriasis data were obtained from GWAS studies with 4,510 psoriasis cases and 212,242 controls.

The researchers found that genetic predisposition to IBD was associated with increased psoriasis risk (odds ratio, 1.1271). A significant association was seen for PsA with total IBD (odds ratio, 1.1202). Causal relationships were also observed for CD-psoriasis and CD-PsA (odds ratios, 1.1552 and 1.1407, respectively). A genetic predisposition to psoriasis was not associated with total IBD; however, psoriasis was associated with CD (odds ratio, 1.2224) but not UC. There was a borderline association observed for genetic predisposition to PsA with IBD (odds ratio, 1.0716), and a suggestive association was observed with CD (odds ratio, 1.0667).

"Understanding that specific types of psoriasis and IBD constitute mutual risk factors facilitates early diagnosis enabling more efficient targeting of therapy," the authors write.

Abstract/Full Text