Hematopoietic stem cell transplantation in sickle cell disease: patient selection and special considerations

Hematopoietic stem cell transplantation remains the only curative treatment currently in use for patients with sickle cell disease (SCD). The first successful hematopoietic stem cell transplantation was performed in 1984. To date, approximately 1,200 transplants have been reported. Given the high prevalence of this disorder in Africa, and its emergence in the developed world through immigration, this number is relatively small. There are many reasons for this; primary among them are the availability of a donor, the risks associated with this complex procedure, and the cost and availability of resources in the developing world. Of these, it is fair to say that the risks associated with the procedure have steadily decreased to the point where, if currently performed in a center with experience using a matched sibling donor, overall survival is close to 100% and event-free survival is over 90%. While there is little controversy around offering hematopoietic stem cell transplantation to symptomatic SCD patients with a matched sibling donor, there is much debate surrounding the use of this modality in "less severe" patients. An overview of the current state of our understanding of the pathology and treatment of SCD is important to show that our current strategy is not having the desired impact on survival of homozygous SCD patients, and should be changed to significantly impact the small proportion of these patients who have matched siblings and could be cured, especially those without overt clinical manifestations. Both patient families and providers must be made to understand the progressive nature of SCD, and should be encouraged to screen full siblings of patients with homozygous SCD for their potential to be donors. Matched siblings should be referred to an experienced transplant center for evaluation and counseling. In this review, we will discuss the rationale for these opinions and make recommendations for patient selection.