From: Macrophage activation syndrome in MDA5 antibody-positive dermatomyositis and COVID-19 infection
A | Molecular diagnosis consistent with HLH associated mutations (PRF1, UNC13D, STX11, STXBP2, Rab27A, SHD1A, BIRC4, LYST, ITK, SLC7A7, XMEN, HPS) |
B | Or 5 of 8 criteria listed below |
1 | Fever ≥  38.5 °C |
2 | Splenomegaly |
3 | Peripheral blood cytopenia, with at least two of the following: hemoglobin < 9 g/dL (for infants < 4 weeks, hemoglobin < 10 g/dL); platelets < 100,000/microL; absolute neutrophil count < 1000/microL |
4 | Hypertriglyceridemia (fasting triglycerides > 265 mg/dL) and/or hypofibrinogenemia (fibrinogen < 150 mg/dL) |
5 | Hemophagocytosis in bone marrow, spleen, lymph node, or liver |
6 | Low or absent NK cell activity |
7 | Ferritin > 500 ng/mL |
8 | Elevated soluble CD25 (soluble IL-2 receptor alpha [sIL-2R]) two standard deviations |