Hemophagocytic syndrome (HPS) is considered to be a histiocytic disease with reactive hyperplasia of the mononuclear macrophage system, also known as hemophagocytic lymphohistocytosis, or hemophagocytic reticulosis. HPS is a macrophage proliferative disease with multiorgan and multisystem involvement and progressive exacerbation with immune dysfunction, representing a group of pathogenically distinct diseases characterized by fever, hepatosplenomegaly, and complete blood cytopenia, which can be detected in bone marrow, spleen, or lymph node biopsies. Phagocytosis is found in bone marrow, spleen or lymph node biopsies. It is a group of clinical syndromes mainly caused by defective cytotoxic killer cells (CTL) and NK cells leading to impaired antigen clearance, excessive activation and proliferation of the mononuclear macrophage system due to continuous antigenic stimulation, and production of large amounts of inflammatory cytokines. Phagocytic syndromes are mainly classified as primary (hereditary or familial) and secondary. Primary HPS is autosomal recessive or X-linked, with a clear genetic defect or family history, and its onset and exacerbation is often associated with infection; secondary HPS can be caused by a variety of factors, including infection (mainly EBV infection), malignancy, autoimmune disease, drugs, and acquired immune deficiency (e.g., transplantation). Secondary HPS includes infection-associated HPS, tumor-associated HPS, and macrophage activation syndrome. There is a lack of specific diagnostic methods. The 2004 diagnostic criteria developed by the International Society of Histiocytes are now widely used and the diagnosis of HPS can be established by meeting one of the following 2 criteria: 1) meeting the molecular diagnosis of HPS with mutations in PRF1, UNC13D, Munc18-2, Rab27a, STX11, SH2D1A or BIRC4; 2) meeting 5 of the following 8 diagnostic criteria (1) fever (2) hepatosplenomegaly and abnormal liver function (blood LDH ≥ normal mean + 3 SD, generally ≥ 1000 U/L); (3) hematocrit (involving ≥ 2 cell lines, no hypoproliferative or abnormal bone marrow proliferation): hemoglobin < 90 g/L (neonatal hemoglobin < 100 g/L), platelets < 100 × 109 /L, neutrophils granulocytes < 1.0 × 109 /L; (4) hypertriglyceridemia and/or hypofibrinogenemia: fasting triglycerides ≥ 3.0 mmol/L (≥ 2.65 g/L), fibrinogen ≤ 1.5 g/L; (5) phagocytosis found in bone marrow, spleen or lymph nodes rather than evidence of malignancy; (6) hypo- or deficient NK cell activity (according to local laboratory indicators) (7) hypoferritinemia (≥ normal mean + 3 SD, usually ≥ 1000 ng/ml); (8) soluble CD25 (sIL-2R) ≥ 2400 U/mL. primary phagocytic syndrome has a poor prognosis with rapid disease progression and early bone marrow transplantation is recommended. In addition to intensive supportive therapy and treatment of complications, there is no specific treatment for primary HPS or patients with undetectable underlying disease, and the fundamental treatment is allogeneic HSCT. The treatment of secondary hemophagocytic syndrome is more complex. The etiology of secondary HPS should be explored and treatment should focus on both the underlying disease and HPS. On the one hand, the primary disease must be treated, for example, chemotherapy for hematologic/lymphatic tumors and anti-infective therapy for infection-associated phagocytic syndrome. Treatment of the primary disease should be accompanied by a phagocytic syndrome regimen to control the progression of the disease. The HLH-2004 regimen for secondary phagocytic syndrome is now commonly used internationally. 2004 is based on dexamethasone, etoposide (VP16) and cyclosporine and is divided into an initial treatment period of 8 weeks and a maintenance treatment period, with additional intrathecal injections. The use of gammaglobulin in the acute phase helps to alleviate the disease. If HPS occurs in a pre-treatment immunodeficient patient, treatment is mainly anti-infective and anti-tumor; if HPS occurs after chemotherapy and the tumor is in remission, anti-tumor therapy should be discontinued and anti-infective therapy with adrenocorticotropic hormone and VP16 should be added; in rapidly progressive MAHS, treatment should target cytokine-induced damage. For rapidly progressive MAHS, treatment should be directed at cytokine damage, using the HLH94 regimen described above. If treatment is difficult, fails, or the disease recurs, bone marrow transplantation may be considered.