Table 1.

Diagnostic criteria for HLH and TMA

Hemophagocytic lymphohistiocytosis (HLH)	Thrombotic microangiopathy (TMA)
A. Genetic HLH diagnosis	A. Tissue diagnosis
or	or
B. Five of the eight criteria met	B. Five of the seven criteria met
1. Fever ≥ 38.5 °C	1. LDH above normal value for age
2. Splenomegaly	2. Schistocytes on peripheral blood smear
3. Cytopenias (affecting at least 2 cells lines) -Hemoglobin < 9 g/dL-Platelets < 100 × 109/L-Neutrophils < 1 × 109/L	3. De novo thrombocytopenia or require platelet transfusions
4. Hypertriglyceridemia and/or hypofibrinogenemia (< 150 mg/dL)	4. De novo anemia or require RBC transfusions
5. Hemophagocytosis	5. Hypertension > 99% for age (< 18 years of age) or 140/90 (≥ 18 years of age) or receiving antihypertensive therapy
6. Low or absent NK cell activity	6. Proteinuria ≥ 30 mg/dL on random urinalysis ×2 or random urine protein creatinine ratio ≥ 2 mg/mg
7. Elevated ferritin > 500 ng/mL	7. Terminal complement activation: elevated plasma sC5b-9 above normal limit of ≥ 244 ng/mL, or elevated above defined normal laboratory value
8. Elevated sIL-2 receptor (sIL2R) > 2400 U/mL or elevated above defined normal laboratory value	Note: 6 and 7 are high-risk TMA features