According to the results of a 2015 study, people with psoriatic arthritis (PsA) may have fewer kinds of microbes in their gut than people with psoriasis alone, suggesting that a lack of microbial diversity could lead to the joint inflammation seen in psoriatic arthritis.
Most scientists agree that psoriatic disease is caused by a combination of genetic and environmental factors. Recently, research into the microbiome—the collection of microbes, or bugs, present in the human body—has raised the possibility that changes in these microbes, called dysbiosis, could be the environmental trigger that sets the immune system into motion, leading to autoimmune diseases such as psoriasis and psoriatic arthritis.
An April 2015 study in Arthritis and Rheumatology investigated the differences in the gut microbiome between people with psoriatic disease and the general population. By analyzing fecal samples from 16 people with psoriatic arthritis, 15 people with psoriasis alone and 17 healthy controls, researchers found that people with psoriasis and psoriatic arthritis have decreased levels of some kinds of microbes, said Dr. Jose Scher, lead author of the study and a rheumatologist at New York University. Some of these microbes, including two kinds known as Ruminoccocus and Akkermansia, are specifically decreased in psoriatic arthritis, he said.
Ruminoccocus and Akkermansia help protect the health of the gut, explained Scher. Without them, the gut may be more prone to inflammation. “It is conceivable that a lack of protection could alter the immune balance in the intestine, ultimately leading to activation of inflammatory cells,” he said. This inflammation could occur locally in the gut, but also in other sites in the body, such as the skin and joints, he added. A similar dysbiosis is seen in inflammatory bowel disease (IBD), noted Scher. Previous research has shown that people with psoriatic disease have an elevated risk for IBD.
According to Scher, because the dysbiosis associated with psoriatic arthritis is different from what is seen in psoriasis, it could potentially serve as a biomarker, or biological sign, of psoriatic arthritis. He and his team now plan to analyze the microbiome of people with psoriasis and psoriatic arthritis to investigate these biomarkers further.
In addition, his team is also planning to study animal models of psoriatic arthritis to explore if replacing the microbes missing in psoriatic arthritis will help improve, or even heal, their symptoms.
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