More patients with MAS-HLH carried BRAF-V600E mutation in lesions or plasma with compared to the patients without MAS-HLH (lesions: 88.0% vs. 63.7%, P = 0.019; plasma: 90.5% vs. 49.0%, P < 0.001, respectively). The gene discussed is BRAF; the disease is hemophagocytic syndrome.