Intriguingly, progressive hemophagocytosis after MMR vaccine or cytomegalovirus infections was noted in two of the previously reported cases [43, 44], as well as in patients with other defects in the type I IFN pathway including STAT1 [49], STAT2 [50, 51], and IFNAR2 [9, 52]. This evidence concerns the gene IFNAR2 and cytomegalovirus infection.