Serum uric acid as a marker of microvascular damage in systemic sclerosis patients

Background: Microvascular damage of skin and internal organs is a hallmark of systemic sclerosis (SSc). Serum uric acid (UA) represents a marker of inflammation and endothelial dysfunction. The aims of this study were to evaluate the correlation between serum UA and intrarenal arterial stiffness evaluated by Doppler ultrasound in SSc patients with normal renal function. We also evaluated the correlation between serum UA and other clinical variables of the disease. Methods: Forty-five SSc patients underwent clinical assessment, Doppler ultrasound of intrarenal arteries with evaluation of resistive index (RI), pulsatile index (PI), and systolic/diastolic ratio (S/D), echocardiography with systolic pulmonary artery pressure (PAPs), baseline pulmonary function tests, and nailfold videocapillaroscopy (NVC). In all patients serum UA was measured. Results: The serum UA showed a significant positive correlation with sCr (r = 0.33, p < 0.0001) and PAPs (r = 0.38, p < 0.01) > and negative correlation with CKD-EPI (r = -0.35, p < 0.01). The mean value of serum UA increased with severity of NVC damage. Using this cut-off value of 4.7 mg/dl, the mean value of Doppler indices of intrarenal stiffness is significantly different (p < 0.05) in SSc patients with low normal or high normal serum UA. Conclusions: Serum UA concentration is higher in patients with high microvascular damage than in patients with low microvascular damage. These preliminary data must be confirmed in large prospective studies.