Human leukocyte antigen matched unrelated donors for patients with sickle cell disease: results of international donor searches

Abstract Sickle cell disease (SCD) is the most common inherited hemoglobinopathy. Hematopoietic stem cell transplantation (HCT) is the only curative therapy for SCD, but few patients will have a matched sibling donor. Patients with SCD are mostly from African origin, therefore less likely to find a matched unrelated donor in international registries. Using HaploStats, we estimated HLA haplotypes for 185 patients with SCD (n=116 from a Brazilian centre; n=69 from the European Society for Blood and Marrow Transplantation (EBMT) centres) and classified the ethnic origin of haplotypes. Next, we assessed the probability of finding a human leukocyte antigen (HLA) matched unrelated adult donor (MUD), considering loci A, B and DRB1 (6/6), in international registries. Most haplotypes were African, but Brazilians showed higher ethnic admixture than EBMT patients. Nevertheless, chances of finding at least one 6/6 potential allelic donor were 47% for both groups. Most potential allelic donors were from the National Marrow Donor Program (NMDP) registry (USA) and from the Brazilian donor registry (REDOME). Although the probability of finding a donor is higher than previously reported, strategies are required to improve ethnic diversity in registries. Moreover, predicting chances of having a MUD might influence SCD management.