The most common causative factor is infection, especially viral infection, and EBV infection is the most common among viral infections; the second causative factor is tumor, mainly lymphoma, in addition, it has been reported internationally that some other tumors can also induce hemophagocytic syndrome when they develop to advanced stage; the third causative factor is rheumatism, although rheumatism does not cause death, some rheumatism appears to be a serious factor. Although rheumatic diseases do not cause death, some rheumatic diseases appear to be very serious because of the possibility of combined hemophagocytic syndrome, and when combined with this disease, rheumatic diseases are a causative factor of hemophagocytic syndrome; the fourth causative factor is organ transplantation, especially solid organ transplantation, such as liver transplantation, kidney transplantation, etc. In addition, hematopoietic stem cell transplantation (i.e. bone marrow transplantation) may also cause hemophagocytic syndrome. . In addition, it is now internationally recognized that some metabolic diseases or drugs can induce hemophagocytic syndrome. Overall, the causative factors of secondary phagocytic syndrome are very complex, and in some patients the cause cannot be identified, and even in special cases, pregnancy or childbirth may induce phagocytic syndrome.