目的：探讨异基因造血干细胞移植(allo-genetic hematopoietic stem-cell transplantation, allo-HSCT)后植入功能不良(poor graft function, PGF)和抗利尿激素分泌不当综合征(syndrome of inappropriate antidiuretic hormone secretion, SIADH)的发病机制及治疗措施。分析本例患儿发病的可能原因。方法：报告1例重型再生障碍性贫血(aplastic anemia, AA)患儿allo-HSCT后临床特点及诊治经过。结果：患儿在allo-HSCT回输干细胞后出现II级超急性移植物抗宿主病(graft versus host disease, GVHD)。+17天突发昏迷、惊厥，完善检查示严重低钠血症，尿钠增多，血浆渗透压下降和尿渗透压升高，诊断为SIADH，经限液、补钠等支持治疗后好转。+15天血象未见明显回升，升白、升血小板治疗效果不佳，考虑原发性PGF。随访至移植后3月余仍需成分输血支持，后每月输注间充质干细胞1次(1 × 106/kg∙次，共3次)及血浆置换2次，达AA基本治愈的标准。结论：Allo-HSCT后PGF和SIADH均为严重的、可能导致不良预后的、威胁生命的并发症，其发病机制仍不明确，已知与和移植相关的多种因素相关。为此分析此病例探讨其机制及治疗措施，以改善患者的预后。 Objective: To investigate the pathogenesis and treatment of poor graft function and syndrome of inappropriate antidiuretic hormone secretion after allogeneic hematopoietic stem cell transplantation, and analyze the possible causes of this case. Methods: The clinical characteristics, diagnosis and treatment of a case of severe aplastic anemia after allo-HSCT are reported. Results: Grade II hyperacute graft versus host disease occurred after allo-HSCT retransfusion of stem cells. 17 days after allo-HSCT after the onset of coma and convulsion, the improved examination showed severe hyponatremia, increased urinary sodium, decreased plasma osmotic pressure and increased urine osmotic pressure. The diagnosis was SIADH, which was improved after supported treatment such as fluid restriction and sodium supplementation. No significant recovery was observed in the blood images for 15 days after allo-HSCT, and the therapeutic effect of white and platelet rising was poor. Primary PGF was considered. The patients were followed up for more than 3 months after transplantation with the support of component blood transfusion. After that, the patients were injected with mesenchymal stem cells once a month (1 × 106/kg∙time, a total of 3 times) and plasmapheresis two times, reaching the standard of AA basic cure. Conclusions: Both PGF and SIADH after allo-HSCT are severe, potentially life-threatening complications with poor prognosis. Their pathogenesis is still unclear and is known to be associated with multiple factors associated with transplantation. Therefore, this case was analyzed to explore its mechanism and treatment measures to improve the prognosis of the patient.