Allogeneic stem cell transplant in primary hemophagocytic lymphohistiocytosis – a single-center experience

Hemophagocytic Lymphohistiocytosis (HLH) is a rare disorder of immune dysregulation characterized by fever, cytopenias, and splenomegaly. Its primary form poses a therapeutic challenge due to its high fatality when left untreated. We retrospectively analyzed 28 patients who underwent related-donor allogeneic stem cell transplant for primary HLH from 2010 to 2021. Among them were 10 cases of familial HLH, 8 cases of Griscelli syndrome type 2, and 1 case each with PRF1 and STX11 mutations. All the patients underwent transplants with reduced-intensity or myeloablative conditioning and 26 of them achieved neutrophil engraftment at a median of day + 14. The donors were either fully matched (68%) or haploidentical (32%). With a median follow-up of 1 year, overall survival was 68% (n = 19) and disease-free survival was 64.4% (n = 18). OS was better in patients transplanted with a sibling donor (compared to parent donor), who achieved complete donor chimerism, and those transplanted early in the course of the disease (diagnosis to transplant duration less than 6 months).