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Data from two large prospective studies confirm earlier suggestions that gout risk is increased among patients with psoriasis and psoriatic arthritis, independent of possible contributing factors such as metabolic syndrome.
Merola JF, Wu S, Han J, et al. Psoriasis, psoriatic arthritis and risk of gout in US men and women. Ann Rheum Dis. (2014) March 20. doi: 10.1136/annrheumdis-2014-205212. [Epub ahead of print]
Especially when they coexist, psoriasis and psoriatic arthritis (PsA) are associated with an increased risk of gout, according to data from two prospective studies of almost 1 million US men and women.
The analysis showed an almost two-fold increased risk for gout among those with self-reported psoriasis, and almost a five-fold increase for those reporting both PsA and psoriasis. The risk was greater risk for men than for women.
The study was based on biennial questionnaires from 27,751 men followed in the Health Professionals Follow-up Study (1986-2010) and 71,059 women tracked by the Nurses' Health Study (1998 to 2010). Among the two cohorts, almost 3,000 people had psoriasis and 2,217 had gout, based on their questionnaire responses.
Data were also obtained from the Psoriasis Screening Tool (PST) and the Psoriatic Arthritis Screening and Evaluation (PASE) questionnaire. Incident cases of gout were documented using the American College of Rheumatology (ACR) gout survey criteria – with 4.9% of the men and 1.2% of women meeting six of the 11 ACR gout criteria.
Those reporting psoriasis appeared also reported higher body mass index (BMI), and were more likely to be smokers or to have type 2 diabetes and/or hypertension treated with diuretics. (Obesity is a gout risk factor and high uric acid levels are associated with use of diuretics.)
Among people with PsA, significant clinical correlations have been found between elevated uremic acid levels and subclinical atherosclerosis, the authors note. Additionally, psoriasis, PsA, hyperuricemia and gout have all been tied to the metabolic syndrome, which increases cardiovascular risk.
However, the association was valid independent of the metabolic-factor variables, the authors said.
“The development of gout, in the setting of hyperuricemia among those with psoriasis and/or psoriatic arthritis, is biologically plausible and supported by our data after adjusting for other known risk factors for gout in this population,” the authors conclude.
Why would these two conditions coexist? Rheumatologists are accustomed to viewing uric acid as a molecule that precipitates from the serum and crystallizes in joints, but monosodium urate crystals have also been found in the skin of patients with tophaceous gout and psoriasis, although the significance of their presence was not clear.
A 2011 study from Japan, reported in the Journal of Immunology, described in vitro and animal studies that suggest a pathway through which monosodium urate released by injured cells in the skin can trigger the release of proinflammatory interleukins.