Serology studies for EBV in 26 episodes from 16 patients showed that 11 HLH patients (ES1-ES6 except ES4 and EM1-EM6) had primary EBV infection with positive anti-VCA-IgM or/and positive anti-EBEA (≥160) (Table 2). Here, CD40LG is linked to Epstein-Barr virus infection.