HAVCR2 and hemophagocytic syndrome: Compared to the prevalence of HAVCR2 mutations (24.5% to 84.6%) and HLH/HLH-like systemic illnesses (17.0% to 63.0%) reported in previous studies among patients with SPTCL of all age groups [5–7, 16, 17], SPTCL in the Thai pediatric population showed a higher burden of underlying HAVCR2 mutations as a predisposing factor for developing SPTCL associated with HLH/HLH-like systemic illnesses in the young.