What is the difference between Multisystem Inflammatory Syndrome in Adults (MIS-A) and MAS/HLH?

Macrophage activation syndrome (MAS)/hemophagocytic lymphohistiocytosis (HLH) are cytokine storm syndromes (CSS) associated with various infections, rheumatic conditions, and hematologic malignancies (among other etiologies). Multi-system inflammatory syndrome in adults (MIS-A) is a discrete entity occurring approximately one month after SARS-CoV-2 infection (believed to be post-infectious) that may share features, or even meet criteria for MAS/HLH. MIS-A is clearly an inflammatory state that can result in multi-organ dysfunction and responds to anti-inflammatory treatments (e.g. glucocorticoids, intravenous immunoglobulin), but not all cases of MIS-A meet a formal definition of MAS or HLH. The pediatric version of MIS-A, MIS-C, typically r...