Haploidentical Stem Cell Transplantation in Childhood

Allogeneic stem cell transplantation has become an important treatment option for many children with malignant and non malignant diseases during the past decades. However, this therapy was for a long time restricted to patients having an “HLA identical donor”. In most recent years donor registries all over the world have extended and the numbers of registered volunteers have substantially increased during the last 20 years. In spite of this progress, there is still a substantial number of children lacking a well matched donor. Virtually all little patients have at least one “haploidentical” parent who could potentially serve as a stem cell donor. These donors are immediately available, are highly motivated and could be asked for a further time if the graft would have been rejected. In the post transplant course parents are repeatedly available for additional donor cell transfusions for preemptive immunotherapy. Moreover using haploidentical parents as donors can avoid the inauguration of new registries and banking expenditures in countries whose population is not very much represented in existing large donor registries. For long years, graft rejection, graft versus host disease (GVHD) and delayed recovery of the immune system used to be the limiting factors for haploidentical transplantation. Substantial progress has been made in the clinical application of haploidentical stem cell transplantation in children with leukemia as well as non malignant diseases in the last years. Recurrence of the underlying disease and delayed immune recovery, however, remained major cause for treatment failure yet to overcome to offer this procedure to a wider range of patients. Nevertheless, haploidentical stem cell transplantation has become a valuable alternative procedure for patients lacking an HLA identical donor. The development and recent advance is reviewed in the following.