Complete response to donor lymphocyte infusion for primary hemophagocytic lymphohistiocytosis relapse after allogeneic hematopoietic cell transplantation

Primary hemophagocytic lymphohistiocytosis (HLH) is a hyper-inflammatory disorder characterized by dysregulation of inflammatory cells and cytokine signalling. Although first-line treatment consisting of immunosuppressive therapy and allogeneic hematopoietic cell transplantation (HCT) is often curative, it remains unknown whether any effective therapies exist for disease relapse/progression after HCT. Here we present a case of a 29-year-old male with primary HLH that relapsed after HCT and subsequently achieved durable long disease-free survival following a donor-lymphocyte infusion (DLI). To our knowledge, this represents the first case demonstrating the efficacy of DLI for relapsed primary HLH.