The class of drugs that are most effective and most often prescribed to treat ulcerative colitis and Crohn’s disease are putting the people who take them at risk for another serious disease—with its own additional health risks. Here’s what you need to know…

Inflammatory bowel disease (IBD) is the term used to describe disorders involving chronic inflammation of the digestive tract, primarily ulcerative colitis and Crohn’s disease. IBD is often treated with a class of drugs called tumor necrosis factor inhibitors—examples are infliximab (Remicade) and adalimumab (Humira). These drugs block a natural substance that triggers inflammation to fight off infection, but which people with IBD have in excess.

TNF inhibitors, created to replace older, less effective medications, work so well for IBD that they are being prescribed more frequently. However, wonderful as these drugs are, more and more IBD patients using the drugs are developing psoriasis, a painful condition that comes with its own additional health risks. In fact, about 40% of IBD patients who develop psoriasis have to stop TNF inhibitor treatment. What is especially puzzling—and ironic—is that TNF inhibitor drugs also are used to treat psoriasis.

Study: To find out more about the risk for psoriasis from TNF inhibitors, researchers at The Catholic University of Korea conducted the first large study to compare IBD patients taking TNF inhibitors with IBD patients who had never taken a TNF inhibitor. Using nearly 10 years of data from a nationwide population sample of more than 50,000 South Koreans diagnosed with IBD, they looked at 5,000 people treated with either infliximab or adalimumab for at least six months and more than 10,000 treated with other medications. No one in the study had psoriasis before starting IBD treatment.

Results: Compared with patients treated with other medications, those who were treated with a TNF inhibitor had more than double the risk of developing psoriasis (3.7% vs 1.5%). Most often they developed palmoplantar pustulosis (which causes redness and pus-filled blisters on the palms and/or soles)…followed by psoriatic arthritis (which causes swollen, stiff joints). Palmoplantar pustulosis also was most common in men (possibly because the disease is more common in smokers, and in Korea most smokers are men, although the study didn’t look at smoking status)…and in both men and women under age 40.

While the study found a higher risk from infliximab, the study authors pointed out that there were too few patients taking adalimumab in the study to draw significant conclusions. Other research finds that psoriasis persists even when switching to a different TNF inhibitor.

Bottom line: TNF inhibitors generally are prescribed long-term. If your doctor prescribes such a drug for your ulcerative colitis or Crohn’s disease, discuss the risk for psoriasis…and ask if one of the older medications might work well enough for you. Also, be sure to let him/her know immediately about any skin changes.