Psoriasis and IBD: What’s the Link?
—German investigators recently set out to determine whether inflammatory bowel disease drives the occurrence of psoriasis or psoriatic arthritis—or whether the reverse is true. Here’s what they found.
A study from Germany appears to confirm prior observations that inflammatory bowel disease (IBD) is a risk factor for the development of psoriasis (PsO)/psoriatic arthritis (PsA).1
“Our findings suggest that IBD seems to be a causal risk factor for psoriasis and psoriatic arthritis, but not vice versa. The exact pathophysiological mechanisms underlying this association are still unknown,” notes Dennis Freuer, PhD, from University Hospital and the University of Augsburg, in Augsburg, Germany. “There seems to be a relationship between gut and skin [gut-skin axis]. However, both the question as well as the direction of a causal relationship had remained unanswered.”
Thousands of genetic samples are evaluated
IBD and psoriatic disease are immune-mediated systemic diseases that impact multiple body systems, with shared pathophysiology involving T helper 17 (Th17) cells and tumor necrosis factor alpha (TNF-α).1 Several immunomodulatory therapies are effective in all 3 diseases: IBD, PsO, and PsA.
In this study, which was published online in JAMA Dermatology, data from across Europe were used to identify genetic samples from individuals with confirmed IBD (n=12,882), or its component diseases Crohn’s disease (CD; n=5956) and ulcerative colitis (UC; n=6968), PsO (n=5621), and PsA (n=2063), as well as a validation sample of self-reported IBD cases (n=7045) and matched controls without immune-mediated disease. A bidirectional, 2-sample mendelian randomization analysis was done using genome-wide association studies (GWAS) and identified single-nucleotide variants (SNVs) associated with each condition. SNVs represented modifiable risk factors and were used to assess causal effects. Total effects were analyzed using univariate mendelian randomization, and individual effects of IBD, CD, UC, PsO, or PsA were analyzed using multivariate mendelian randomization.
Other analyses were done to determine directional effects and to rule out confounding effects. Outcomes represented genetically predicted risk for psoriatic disease with existing IBD and for IBD with existing psoriatic disease.
IBD increases risk for PsO/PsA
The analyses revealed a causative relationship between IBD and risk for PsO/PsA, but not the reverse.1
- In a meta-analysis of the univariate data, the odds ratio (OR) of PsO development with IBD was 1.10 (95% confidence interval [CI] 1.05 to 1.15; P<.001) and the OR of PsA development was 1.11 (95% CI 1.04 to 1.18; P=.003).
- In reverse, however, neither existing PsO (OR 0.98, 95% CI 0.95 to 1.02) nor existing PsA (OR 1.01, 95% CI 0.91 to 1.13) was associated with elevated risk for IBD.
- In a multivariate analysis, CD, but not UC, was significantly associated with development of PsO and PsA. No causative relationship in the opposite direction was identified.
“Prior to our study, a link between IBD and psoriasis was suspected based on observational studies,” Dr. Freuer explains. Results of this study, however, show that, “in particular, the sub-entity Crohn’s disease seems to be associated with the development of both outcomes.” Sensitivity analyses confirmed the reliability of the results.
Not the end of the research road
There’s still much to be learned about the relationship between these diseases, Dr. Freuer concedes. Population cohort and other studies have reported the IBD-psoriasis relationship, including some that showed an increased risk for CD or UC in patients with psoriasis, in contrast to the current results. The present study builds on previous work by establishing a causal link between IBD and psoriatic disease, no doubt related to shared aspects of pathophysiology. For those in the clinic, this information can provide useful guidance when evaluating patients with IBD.
“Our results are critical, because raising awareness among clinicians about the potential risk of psoriasis in patients with IBD will contribute to systematic diagnosis and interdisciplinary and early personalized treatment of patients,” Dr. Freuer concludes. “Treating physicians should keep an eye out for skin changes in patients with IBD and consider the possible manifestation of psoriasis early on, so that adequate therapy can be initiated at an early stage.”
Published:
References
.jpg)