Microscopic Colitis Patients Almost Twice as Likely to Develop Psoriasis

David Bergman, PhD

Credit: Karolinska Institutet

Individuals with microscopic colitis (MC) pose an almost double risk of developing psoriasis versus individuals within the general population, according to new findings, and physicians may seek to consider psoriasis in patients with microscopic colitis and lesions on their skin.¹

These findings were the conclusion of a recent nationwide study led by David Bergman, PhD, from the department of medical epidemiology and biostatistics at the Karolinska Institutet in Stockholm, Sweden.

Bergman and colleagues noted that microscopic colitis had been previously linked to a set of immune-mediated conditions such as psoriasis, though they added that earlier research had been limited to psoriasis taking place prior to microscopic colitis. Large-scale cohort study data assessing this condition and its associated risk of future development of psoriasis were noted as lacking.

“As MC and psoriasis are both immune-mediated diseases, with known associations to several autoimmune disorders and since both conditions have been linked to genes coding for the major histocompatibility complex, we hypothesized that a correlation between the two disorders exists,” Bergman and colleagues wrote. “Thus, this project aims to elucidate the association between MC and future psoriasis in a large, nationwide matched cohort study.”^2,3

Background and Methods

The investigators gathered the necessary data for this nationwide matched cohort study from several different Swedish healthcare registers as well as government-maintained registers of population. Their period of study was initiated on January 1, 2007, with the research team assessing data from the Prescribed Drug Register since the register’s inception in 2005 to evaluate subjects’ criteria for eligibility.

For those that had microscopic colitis, their conditions were identified by the team through the use of the relevant Systematized Nomenclature of Medicine (SNOMED) codes from the ESPRESSO trial. The team used a validation study to verify the accuracy of the method.

Subjects without psoriasis or microscopic colitis used as reference individuals were determined by the investigators using individuals from the general population, and they used matching criteria from the Total Population Register such as year of birth, sex, county of residence, and index year.

Those who were full siblings and who lacked a previous diagnosis of microscopic colitis were found by the research team through use of the Multi Generation Register, which made it so that comparisons of their shared genetics and early environmental influences could be found. Psoriasis as an outcome was defined by the team through ICD-codes in the National Patient Register (NPR), and follow-up began by the time of diagnosis of microscopic colitis or corresponding dates for those who were used for reference. Follow-up carried on until the end of December 2021, or up until death, psoriasis diagnosis, or emigration.

Findings

There was a median follow-up time of 9.2 years and over this time, the investigators found that there were 179 individuals with microscopic colitis. They found that 440 reference individuals were shown to have developed cases of psoriasis, with these numbers corresponding to a rate of 241.1 events per 100,000 person-years for those with microscopic colitis and 131.8 events per 100,000 person-years for those used as references.

In other words, around 1 additional case of psoriasis was identified in every 91 subjects that had microscopic colitis over the course of a decade. The research team adjusted for matching variables and level of subject education, and then the adjusted hazard ratio (aHR) was reported by the team to be 1.82 (95% CI = 1.53–2.17).

They also found that when stratified by subjects’ sex, their estimates of the conditions had stayed consistent. There were also substantially higher aHRs reported by the investigators up to 10 years post diagnosis of microscopic colitis, and when compared to siblings without the condition, the aHR had been 1.85 (95% CI = 1.36–2.51).

“Previously, and to the best of our knowledge, the association between MC and psoriasis has only been investigated in two studies focusing on psoriasis (among other conditions) as a risk factor for MC,” they wrote. “...In addition, none of these studies reported stratified analyses or sensitivity analyses. However, the reported ORs are in line with the higher proportion of exclusions due to previous psoriasis in our MC population compared to the reference population.”

References

1. ^{Bergman D, Roelstraete B, Sun J, Ebrahimi F, Lidström R, Svedbom A, Ståhle M, Ludvigsson JF. Microscopic Colitis and Risk of Incident Psoriasis: A Nationwide Population-Based Matched Cohort Study. Clin Epidemiol. 2024;16:213-225. https://doi.org/10.2147/CLEP.S454677.}
2. ^{Westerlind H, Mellander MR, Bresso F, et al. Dense genotyping of immune-related loci identifies HLA variants associated with increased risk of collagenous colitis. Gut. 2017;66(3):421–428. doi:10.1136/gutjnl-2015-309934.}
3. ^{Winchester R, Minevich G, Steshenko V, et al. HLA associations reveal genetic heterogeneity in psoriatic arthritis and in the psoriasis phenotype. Arthritis Rheum. 2012;64(4):1134–1144. doi:10.1002/art.33415.}