Mixed chimerism following hematopoietic stem cell transplantation in pediatric thalassemia major patients: a single center experience.

OBJECTIVE Stable mixed chimerism (MC) may result in cure for thalassemia major patients following hematopoietic stem cell transplantation (HSCT), but rejection can occur. Twenty-eight HSCTs for thalassemia major were reviewed retrospectively to evaluate the clinical course of MC with possible risk factors and predictors of outcome, with a median follow-up of 1669 days (811-3576 days). METHODS Chimerism was detected by fluorescence in situ hybridization (FISH) or multiplex polymerase chain reaction depending on the sex match between the donor and the recipient. RESULTS Primary rejection, stable MC and full donor chimerism was detected in 3.6%, 17.8% and 78.6% of patients, respectively. Clinically, 4/5 patients with stable MC had thalassemia trait with donor chimerism as low as 14%. One patient was started on pRBC transfusions at 2.5 years postHSCT. CONCLUSION Stable MC can result in cure for thalassemia major patients. The clinical picture remains as the best guide for intervention until a more reliable predictor is available.