Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2015.179 Figure 3 Multi-layer model of pathogenic events leading to the development of MAS in the context of rheumatic diseases Figure 3 | Multi-layer model of pathogenic events leading to the development of MAS in the context of rheumatic diseases. Genetic factors and the inflammatory milieu created by the underlying rheumatic disease act synergistically to reach the threshold for macrophage activation syndrome (MAS) in the presence of an infectious trigger. Grom, A. A. et al. (2016) Macrophage activation syndrome in the era of biologic therapy Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2015.179