An investigation into the link between psoriasis and gout.
INTRODUCTION
Gout is a type of inflammatory arthritis that affects 0.08% of the global population.1 It has symptoms that tend to flare every so often, developing over a few hours and causing severe pain in the joints. It is caused by deposits of crystals of a substance called uric acid (urate) in the joints, which leads to inflammation. Psoriasis is a chronic inflammatory skin disease, and up to 25% of these patients may have associated joint disease (psoriatic arthritis). People with psoriasis and psoriatic arthritis often have high levels of uric acid in their blood, which may increase with the severity of their disease. These high levels of uric acid may mean they are more likely to develop gout than people without psoriasis.
WHAT DID THE AUTHORS HOPE TO FIND?
The authors hoped to find out whether patients with psoriasis or psoriatic arthritis have a higher risk of developing gout than normal healthy people.
WHO WAS STUDIED?
The study included 98,810 people with psoriasis and/or psoriatic arthritis from two large groups of men and women living in the United States of America who had agreed to have elements of their health measured regularly over the course of many years in either the Nurses’ Health Study or the Health Professionals Follow-up Study.
HOW WAS THE STUDY CONDUCTED?
The Nurses’ Health Study and the Health Professionals Follow-up Study were two large observational cohort studies that collected medical information every 2 years over several decades. This means that the groups of people in the studies had no medical intervention, but simply completed regular questionnaires and had information about their medical history and lifestyle collected in large databases, which allowed researchers to investigate how common different diseases are and to try to work out if there are certain links or risks between any of them. For this particular study, the authors looked at people within the groups who reported on their questionnaires that they had been diagnosed with psoriasis and/or psoriatic arthritis, and then found out how many of those patients went on to report incidences of gout.
WHAT WERE THE MAIN FINDINGS OF THE STUDY?
The authors found that the risk of developing gout was nearly twice as high in patients who had psoriasis, and tended to be higher in men than women. There was a much higher risk for patients who had both psoriasis and psoriatic arthritis – these people were five-times more likely to develop gout than people without psoriasis or psoriatic arthritis.
ARE THESE FINDINGS NEW?
Yes – it has been suspected before that psoriasis and gout might be linked, but this is the first time it has been investigated in a large group of patients. These new findings have important implications for how doctors look after and monitor patients with psoriasis or psoriatic arthritis. This new information should remind doctors to think about gout as a possible cause of inflamed and painful joints in psoriasis patients.
HOW RELIABLE ARE THE FINDINGS?
While this study has many strengths, including the very large number of patients and the way in which diagnoses were confirmed, there are some limitations. One important limitation is that the results rely on questionnaires and self-reporting by the patients to provide information about their skin and joint diseases. Additionally, there were no blood samples from the patients to allow the authors to determine whether there was any association with elevated uric acid levels (the known cause of gout) or other factors such as kidney function.
WHAT DO THE AUTHORS PLAN ON DOING WITH THIS INFORMATION?
The authors hope to work more on investigating the underlying mechanisms between gout and psoriasis or psoriatic arthritis.
WHAT DOES THIS MEAN FOR ME?
We know that uric acid is linked to the risk of developing gout, and this study shows that patients with psoriasis – and particularly those with both psoriasis and psoriatic arthritis – are more likely to develop gout than other people might be. Doctors should consider gout as a possible cause of joint pain in patients with psoriasis. If you have psoriasis, it may be worthwhile talking to your doctor about ways to reduce your uric acid levels, as this may reduce the risk of developing gout in the future. It is possible that losing weight, stopping smoking and avoiding drinking too much alcohol could help to reduce the severity of gout flares in patients who already have the condition.
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Date summary prepared: August 2015
Summary based on research article published on: 13th October 2015
From: Merola, JF. et al. Psoriasis, psoriatic arthritis and risk of gout in US men and women. Ann Rheum Dis 2015;74:1495–1500. doi:10.1136/annrheumdis-2014-205212LaySummary
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ADDITIONAL REFERENCES
1 Smith E., et al. The global burden of gout: estimates from the Global Burden of Disease 2010 study. Ann Rheum Dis 2014;73:968–74
