Psoriasis, psoriatic arthritis connected to Crohn’s 

| Beth Orenstein

Amanda Leishman, 23, has had psoriasis since she was 3. 

About three years ago, the resident of South Central England started passing blood when she went to the bathroom.

“Any time I ate even the smallest amount, I had to immediately go the bathroom,” she said. 

Leishman confided in her brother, who told her the symptoms sounded similar to those he had when he was diagnosed with Crohn’s disease a year earlier. 

Leishman’s doctors confirmed the Crohn’s diagnosis after a colonoscopy but did not suggest a connection between her psoriasis and Crohn’s. However, following the diagnosis in 2010, her own research confirmed the possibility that the two autoimmune diseases could be linked. 

Researching a connection

Dr. Abrar A. Qureshi, a dermatologist at Harvard and Brigham and Women’s Hospital in Boston, also suspected a connection. He had noticed a number of patients had both psoriasis and Crohn’s, leading him to wonder whether he could find a connection and, if he did, why that was the case. 

Qureshi said he wasn’t surprised when the preliminary results of his prospective study published in the Annals of Rheumatic Diseases in April suggested an association between psoriasis and inflammatory bowel disease, of which Crohn’s is one. 

With Crohn’s, as with psoriasis, the body mistakes healthy tissue for a foreign invader and attacks it. Crohn’s creates chronic inflammation of the intestinal wall at anywhere in the intestinal track, from the mouth to the rectum, which causes the wall to thicken.

Symptoms of Crohn’s include diarrhea, abdominal pain, cramping, bloody stools, reduced appetite and weight loss, and can be mild to severe. And, as with psoriasis, symptoms can come and go with periods of flares. 

To conduct the study, Qureshi and his colleagues analyzed data from the Nurses’ Health Study (NHS) and NSH II, which had more than 174,000 participants. (The NHS is the world's largest, longest-running study of women's health.) The investigators identified women who had psoriasis when they enrolled and who reported developing inflammatory bowel disease in follow-up questionnaires. The investigators then confirmed the diagnoses with medical records and follow-up reports from both NHS studies.

The researchers identified approximately 4,400 women who had psoriasis at the start of their studies. During their follow-up, investigators found that 423 participants (about 10 percent) had developed Crohn’s disease (187) or ulcerative colitis (236), another type of inflammatory bowel disease. 

“When we looked to see who had both conditions, we found a statistically significant number of women had psoriasis and Crohn’s,” Qureshi said.

The link strengthens

The women who developed Crohn’s had first been diagnosed with psoriasis. 

“This tells us that people with psoriasis have an increased risk of developing Crohn’s disease later in life,” Qureshi said. 

The researchers also found that patients who had psoriasis and psoriatic arthritis, such as Leishman, who was diagnosed with the latter about a year ago, were at even higher risk of developing Crohn’s. 

Qureshi said findings from gene and molecular research may explain the connection. Scientists have long known that psoriasis and Crohn’s disease have a number of polymorphisms (genetic mutations) in common, he said. The same genes that make a person susceptible to psoriasis may also make that person susceptible to Crohn’s.  

Genes encode cytokines, substances that are secreted by the cells of the immune system. Cytokines are messengers; they carry messages between cells and thus have an effect on other cells.  Researchers have identified two cytokines — interleukin 12 (IL-12) and interleukin 23 (IL-23) — that they believe can cause abnormal activity in the body’s immune system in some people. One of the FDA-approved therapies for plaque psoriasis is Stelara (ustekinumab) that interferes with IL-12 and IL-23. Stelara also has shown to decrease the debilitating effects of Crohn's disease in some patients. 

Qureshi said more research needs to be done, but the findings to date should remind dermatologists to ask patients with psoriasis — and especially those who also have psoriatic arthritis — if they’re having any bowel symptoms. 

“In the study we published, it’s psoriasis patients who develop Crohn’s later on in life, which is why the onus is on us as dermatologists to make sure we ask,” he said.  Patients with symptoms should be referred to gastroenterologists, just as patients who show symptoms of psoriatic arthritis should be referred to rheumatologists, Qureshi said.

Psoriasis, PsA raise the risk

Dr. Leyla Ghazi, a gastroenterologist at the University of Maryland Medical Center and a member of the patient education committee of the Crohn’s & Colitis Foundation of America, said she has found psoriasis to be one of the most common chronic comorbidities in patients with inflammatory bowel disease, “and that the presence of psoriasis increases the risk for developing IBD."

Some days, Leishman’s Crohn’s flares, some days it’s her plaque psoriasis and others it’s her psoriatic arthritis. She said she is researching different biologics to discuss with her specialists and is hoping to find one that will help with all of her symptoms. 

Having Crohn’s is worse than having psoriasis because “people can’t see it and don’t know just how physically draining it can be,” Leishman said.

Even after 20 years, she still gets the same questions about her psoriasis: “Is it contagious?” or, “Did you burn yourself?” But her biggest concern, she said, is whether her future children will be susceptible to Crohn’s and psoriasis, as well.

By then, perhaps, medical science will have a better understanding of the correlation and how to treat the co-existing conditions.

Driving discovery, creating community

For more than 50 years, we’ve been driving efforts to cure psoriatic disease and improve the lives of those affected. But there’s still plenty to do! Learn how you can help our advocacy team shape the laws and policies that affect people with psoriasis and psoriatic arthritis – in your state and across the country. Help us raise funds to support research by joining Team NPF, where you can walk, run, cycle, play bingo or create your own fundraising event. If you or someone you love needs free, personalized support for living a healthier life with psoriatic disease, contact our Patient Navigation Center. And keep the National Psoriasis Foundation going strong by making a donation today. Together, we will find a cure.

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