A 10-year-old girl was diagnosed with AML (M4); chromosome: chromosome:46, XX; negative fusion gene; Izkf1 negative; full exon sequencing: a frameshift mutation was detected in WT1 gene; RNA SEQ detected after the fusion gene: PRDM16/SKI positive. The patient received induction chemotherapy with daunorubicin, cytarabine, cytarabine, and etoposide (DAE) scheme in June 2020 and achieved a partial response (PR). Then, the patient received consolidation chemotherapy with idarubicin, cytarabine (IA) scheme, and 2 cycles of dicitabine, homoharringtonine, cytarabine, and recombinant human granulocyte colony-stimulating factor (G-CSF) (DEC + HAG) scheme and achieved a PR. After receiving dicitabine, cladribine, cytarabine, and G-CSF (DEC + CLAG) scheme, the patient achieved a complete response (CR); at this stage, the patient was positive for minimal residual disease (MRD), confirmed through flow cytometry (FCM). The patient underwent allo-HSCT from a HLA-mismatched related donor (5/10), after preconditioning with semustine, CLAG, cyclophosphamide, busulfan (CCNU + CLAG + BuCy), followed by cyclosporine A, mycophenolate mofetil, and short-term methotrexate for prophylaxis of GVHD. The patient achieved CR with MRD negativity (CRMRD-) 1 month after allo-HSCT and no GVHD. In May 2021, 4 months after HSCT, the disease progressed to relapse, and the evaluation of bone marrow (BM) showed that 16.5% of blasts, 84.6% of donor chimeric; 32.29% of FCM-MRD; and 7.57% of WT1. We performed the HLA-loss test, but no HLA gene loss was detected. So the patient was treated with azacytidine chemotherapy and DLI, but it was still not achieved CR. The second transplantation was performed 5 months after HSCT1. The patient underwent allo-HSCT from a HLA-mismatched unrelated donor (cord blood) (7/10), after preconditioning with total body irradiation (TBI), CLAG, mefallen, followed by cyclosporine A, mycophenolate mofetil, and short-term methotrexate for prophylaxis of GVHD. The patient achieved CR MRD 1-month after allo-HSCT and no GVHD. The patient was treated with azacytidine and interferon for preemptive therapy, but after that, the patient achieved CR MRD, but the copy number of WT1 in the patient increased gradually. Three months after the HSCT2, the patient was treated with azacytidine and camrelizumab (3 mg/kg/d) injection. On that day, the child felt general pain and discomfort, low fever, gradually developed a skin rash, even blisters, diarrhea, dark green watery stool, jaundice, abnormal liver function, 4-degree GVHD, accompanied by repeated fever hyperferrinemia, hypofibrinogenemia, hypertriglyceridemia, cytopenias, and sIL-2R > 2500 pg/ml (Table 1), which was consistent with sHLH. The children were combined with four degrees of GVHD and sHLH and were gradually reduced and treated with methotrexate (MTX) and MP (5 mg/kg/d), and basiliximab. GVHD and sHLH were gradually controlled. The evaluation of bone marrow (BM) showed CR, no hemophagocyte was found, and the copy number of WT1 decreased.