Chimerism in pediatric hematopoietic stem cell transplantation and its correlation with the clinical outcome

Hematopoietic stem cell transplantation (HSCT) is the only hope to cure many inherited and acquired hematological disorders in children. Monitoring of chimerism helps to predict the post-transplantation events, with the intention to enhance the long-term disease free survival (DFS). The study aimed to investigate the importance of early chimerism detection to predict the clinical outcome following HSCT. The study included nine recipients (six β-thalassemia and three severe aplastic anemia patients) and their 10/10 HLA identical sibling donors. Chimerism detection was performed by analysis of short tandem repeat (STR) polymerase chain reaction (PCR) for detection and quantification of the relative amounts of donor and recipient cells present on day + 28. Peripheral blood (PB) was the main stem cell source for HSC transplantation. Disease free survival (DFS) was 71.4% while overall survival was 85.7% for PBSC transplants at the median follow up period of 4 years. The early detection of chimerism by PCR-STR analysis for children with β-thalassemia and aplastic anemia correlated with the outcome of HSCT in 8 (88.8%) patients. Complete chimerism was associated with disease-free survival while mixed chimerism and autologous patterns were associated with poor prognosis. In conclusion, early chimerism testing is clinically important in prediction of outcome after allogeneic HSC transplantation.