Some Rheumatoid Arthritis Patients Have Elevated Monosodium Urate Deposits

A study in Seminars in Arthritis & Rheumatism suggests that a considerable number of patients who suffer from rheumatoid arthritis (RA) display periarticular monosodium urate (MSU) deposits.

The findings are potentially important because while the differences between the presentation, etiology, and pathophysiology between gout and RA are generally well-understood, there is currently no known single cause for RA. Recent improvements in imaging techniques that detect urate disposition may allow clinicians to target hyperuricemia before crippling symptoms even begin, and may get researchers to a deeper understanding of what specific factors cause RA. Early treatment of gout, RA, and other inflammatory diseases is widely considered to be essential for the growing number of patients who suffer from them.

In the current prospective study, 100 consecutive patients with RA and a serum urate level above 6 mg/dl underwent dual energy computed tomography (DECT) of both feet and hands to search for MSU crystals. The presence and proliferation of MSU crystal deposits on the test was assessed by automated volume measurement. Demographic information and disease-specific characteristics were recorded and included into logistic regression models to test for the factors associated with MSU crystal deposits in RA.

Those RA patients with hyperuricemia were mostly male (55%), over 60 years of age (63±11 years), had established disease (8.7±10.5 years), and had a mean disease activity score 28 (DAS 28) of 3.2. Twenty out of 100 patients displayed MSU crystal deposits in DECT.

The study may also contribute to the growing understanding about how seropositive and seronegative cases of RA progress and how they can be treated. In the current study, the majority (70%) of the RA patients positive for MSU crystal deposits were seronegative RA patients. Every third seronegative RA patient had MSU crystal deposits. According to logistic regression model analysis, seronegative status correlated positively with presence of urate deposits (p=0.019).

Gout tends to be more treatable than RA, but further research into the role and behavior of MSU crystal deposits could lead to enhancements in RA care. The researchers would like to see larger clinical studies that further establish the connection between MSU crystals and some RA cases.