Neutrophil counts >1.8 × 109/L (sensitivity 85 %, specificity 83 %), CRP >90 mg/L (74 %, 89 %) and sCD25 < 7900 U/ml (79 %, 76 %) indicated MAS in sJIA rather than primary HLH or VA-HLH. The gene discussed is CRP; the disease is hemophagocytic syndrome.