Case report: emapalumab treatment for a pediatric Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) patient with cytokine storm enabling allogeneic hematopoietic cell transplantation.

Background:Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome characterized by excessive immune activation and inflammatory response. Conventional immunotherapy and molecular targeted drugs demonstrate varying efficacy. Cytokine storm, the primary pathogenic mechanism of HLH, is driven by interferon-gamma (IFN-γ), interleukin (IL)-2, IL-18, etc., in which IFN-γ plays a critical role in the development of the disease. Emapalumab, a potent IFN-γ inhibitor, effectively reduces the occurrence of cytokine storms in refractory and relapsed HLH. Case Description:A pediatric patient, 5 years old, female, with relapsed and refractory Epstein-Barr virus-associated HLH (EBV-HLH) showed no response to conventional chemotherapy or molecular-targeted drug treatment. However, after treatment with emapalumab, the patient achieved hematological remission. Subsequently, the patient underwent allogeneic hematopoietic cell transplantation (allo-HCT) and remains without HLH to date. Conclusions:To the best of our knowledge, this is the first case report using emapalumab to control EBV-HLH before HCT in mainland China. This case highlights the potential efficacy of emapalumab for treating relapsed and refractory EBV-HLH and providing a stable physical status for HCT. Further research is necessary to confirm the efficacy and safety of emapalumab in this setting.