MLVtotal of LNs > 62.2 had a sensitivity of 80.0%, a specificity of 93.9%, and an AUC of 0.855 in predicting MAS occurrence, which were comparable with those of the traditional marker, IL-2R (sensitivity, 75.0%; specificity, 97.3%; AUC, 0.899). This evidence concerns the gene IL2RA and macrophage activation syndrome.