APOM and endothelial dysfunction: In patients 20–45 years of age, no association was seen between RHI and plasma concentrations of HDL or LDL (r = − 0.04, p = 0.76, beta = − 0.08, 95% CI − 0.58–0.43, and r = 0.25, p = 0.07, beta = 0.18, 95% CI − 0.02–0.38, respectively), suggesting that apoM is a superior marker of endothelial dysfunction in young SLE patients.