FCGR2A and macrophage activation syndrome: Table 2 depicts the fold change expression of FCGR genes and CD163 from each patient with MAS. The consistent pattern of overexpression of FGRP correlated with the increased phagocytosis in MAS mice and hemophagocytosis in patients with MAS. IL-12 production pathway was not significantly altered in patients with MAS (Figure 8A).