Microscopic colitis a risk factor for rheumatoid arthritis

Individuals with microscopic colitis have a twofold greater risk of rheumatoid arthritis (RA) compared with those in the general population, as reported in a study.

The study included 8,179 patients with biopsy-verified microscopic colitis in Sweden and 36,400 matched reference individuals and 8,202 siblings without microscopic colitis. Data on microscopic colitis were collected from all of Sweden's regional pathology registers through the ESPRESSO cohort, while the incidence of RA was ascertained using data from the National Patient Register.

Over a median follow-up of 9.1 years, RA was diagnosed in 73 microscopic colitis patients and 183 reference individuals from the general population, corresponding to incidence rates of 99 and 55 events per 100,000 person-years, respectively. These numbers were equivalent to one extra case of RA in 226 patients with microscopic colitis followed for 10 years.

Multivariable Cox regression showed that microscopic colitis was associated with an 83-percent increased risk of incident RA (adjusted hazard ratio [aHR], 1.83, 95 percent confidence interval [CI], 1.39–2.41).

The risk increase was highest during the first year of follow-up (aHR, 2.31, 95 percent CI, 1.08–4.97) and remained significantly elevated up to 5 years after microscopic colitis diagnosis (aHR, 2.16, 95 percent CI, 1.42–3.30).

Results of the sibling analysis followed a similar pattern, with microscopic colitis being associated with a twofold greater risk of developing RA (aHR, 2.04, 95 percent CI, 1.18–3.56).

The present data may help accelerate the evaluation for RA in patients with microscopic colitis presenting with joint symptoms and/or arthralgia, according to the researchers.