Modified G‐CSF/ATG‐Based Haploidentical Transplantation Protocol in Pediatric Primary Hemophagocytic Lymphohistiocytosis: A Long‐Term Follow‐Up Single‐Center Experience

Background Primary hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome caused by immune dysregulation. Hematopoietic stem cell transplantation (HSCT) represents the only option for long‐term cure for primary HLH. However, only around 25% of patients have a fully HLA‐matched donor. Methods In this retrospective study, we analyzed 42 pediatric patients with primary HLH who underwent haplo‐SCT using the modified granulocyte colony‐stimulating factor (G‐CSF)/antithymocyte globulin (ATG)‐based protocol. The conditioning regimen included 300–600 mg/m 2 etoposide (VP16), along with low doses of busulfan (Bu) (0.8–1.2 mg/kg every 6 hours on Days −8 to −6), cyclophosphamide (Cy) (10 mg/kg/day on Days −4 to −3), fludarabine (Flu) (30 mg/m 2 /day on Days −5 to −3), and ATG (8–9 mg/kg total dose on Days −5 to −2) to reduce complications. Results All 42 patients achieved successful engraftment. Following a median follow‐up period of 48.7 months, 32 of the 42 patients remained alive and disease free. The 2‐year overall survival (OS) rate was 78.4%, and the 5‐year OS rate was 73.7%. The 2‐year failure‐free survival (FFS) rate was 71.3%, and the 5‐year FFS rate was 66.5%. Patients who achieved complete remission at the time of HSCT showed better OS ( p < 0.05). The incidence of Grade III–IV acute graft‐versus‐host disease (GVHD) was 26.2%, and severe chronic GVHD was observed in 11.9% of patients. Thrombotic microangiopathy occurred in 13 patients, and veno‐occlusive disease in two patients. Conclusions This modified G‐CSF/ATG‐based haploidentical protocol demonstrates significant potential for pediatric patients with primary HLH, exhibiting commendable effectiveness and safety.