Increased serum uric acid levels are associated with digital ulcers in patients with systemic sclerosis

Endothelial injury/dysfunction is thought to be one of the earliest events in the development of vascular diseases in systemic sclerosis (SSc). Although hyperuricemia is also known to induce endothelial dysfunction and vascular inflammation, the effect of uric acid on the microvascular involvement in SSc has not been well established. We investigated whether increased serum uric acid (SUA) levels are associated with digital ulcers (DUs) in SSc. In this cross-sectional study, we consecutively recruited 71 women with SSc and 349 age- and sex-matched healthy subjects, and SUA levels were measured in all study subjects. SSc patients had significantly higher mean SUA levels than healthy subjects (4.5 ± 1 mg/dL vs 4.2 ± 0.9 mg/dL, p = 0.017), although a significantly lower body mass index (BMI) was observed in SSc patients than in controls. Among 71 SSc patients, 22 (31%) had DUs ever (active DUs, 8; healed DUs, 14). SSc patients presenting with DUs ever showed significantly higher SUA levels than those without this feature (median, 5.2 mg/dL vs 4.1 mg/dL, p = 0.009). In multivariable logistic regression models adjusted for confounders such as BMI and estimated glomerular filtration rate, increased SUA levels were associated with a significantly higher risk for the presence of DUs ever (OR 2.3, 95% CI 1.16-4.57, p = 0.018). Our data revealed that elevated SUA levels are independently associated with the presence of DUs in SSc patients, thereby suggesting the potential role of hyperuricemia in the pathogenesis of SSc vasculopathy.