Psoriasis and Psoriatic Arthritis Linked to Increased Gout Risk
Study findings could have practical applications for people with these related diseases.
Doctors have noticed a connection between psoriasis, psoriatic arthritis and gout for decades. The common denominator, they have found, is uric acid. Uric acid is a substance that forms when the body breaks down purines, which are found in human cells and many foods.
In gout, uric acid builds up in the joints and tissue around the joints – often the big toe – and forms needle-like crystals, which can cause sudden episodes of intense pain and swelling. If left untreated, gout can become chronic and lead to joint damage. In psoriasis and psoriatic arthritis, uric acid is thought to be a byproduct of rapid skin cell turnover and systemic inflammation.
Confirming the Uric Acid Connection
In a study published in 2014 in Drug Development Research, Italian researchers who examined blood levels of uric acid in 338 psoriasis patients found that hyperuricemia (abnormally high levels of uric acid in the blood) affected 20 percent (67 out of 338) of patients with psoriasis.
In a separate study published in the same year in the Journal of the American Academy of Dermatology, the same group of researchers studied 119 people with psoriasis and 119 people without the disease. They found that patients with psoriasis were three times as likely to have hyperuicemia as controls. After adjusting for age, sex and other factors, psoriasis was the strongest predictor of hyperuricemia.
A large study, also published in 2014, supports the connection between high uric acid levels and psoriasis and suggests an especially strong connection with psoriatic arthritis. Published in Annals of the Rheumatic Diseases, the study drew a total of almost 99,000 participants – nearly 28,000 men and 71,000 women – from two large databases. All participants completed questionnaires about their medical history and lifestyle risk factors at the start of the study and at regular intervals throughout. During the follow-up periods, 4.9 percent of men and 1.2 percent of women developed gout.
After controlling for variables that can contribute to the development of gout, researchers found that the risk of developing gout was roughly twice as high in men and one-and-a-half times as high in women who had psoriasis than in those who didn’t. For men and women with both psoriasis and psoriatic arthritis, the risk of developing gout was nearly five times greater compared to participants with no psoriasis or psoriatic arthritis.
Connection Doesn’t Necessarily Mean Cause
Researchers are cautious in suggesting that psoriasis and psoriatic arthritis actually cause gout, however. “Our findings suggest that there is a causal link between psoriasis, psoriatic arthritis and gout, but we can only say there is an association,” says the study’s lead author, Joseph Merola, MD, co-director of the Center for Skin and Related Musculoskeletal Diseases at Brigham and Women's Hospital in Boston.
How Findings May Help
Still, the findings are important for a number of reasons, researchers say. For one, they can alert doctors to the possibility of a gout diagnosis when people with psoriasis or psoriatic arthritis complain of extreme joint pain or recurrent tender, swollen joints. “We can check serum uric acid levels or make a diagnosis by putting a needle into a joint and extracting some fluid for analysis,” says Dr. Merola.
Another reason is that treatment to control psoriatic arthritis could potentially be useful against gout, or that strategies to prevent gout are important for people with psoriasis or psoriatic arthritis.
“It certainly adds to our clinical observation and current knowledge,” says Jasvinder Singh, MD, a rheumatologist and associate professor in the division of clinical immunology and rheumatology at the University of Alabama, Birmingham. “If physicians and patients are aware of the high risk of gout in psoriasis, they might use preventive strategies – such as diet and lifestyle changes – to reduce the risk. How much we can reduce risk by changing diet and lifestyle remains to be seen, but we can employ that strategy.”
Further research may help scientists understand both diseases and the mechanisms as to how and why the risk of gout exists, Dr. Singh says.
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