Sibling HLA-matched cord blood transplant for β-thalassemia: Report of two cases, expression of fetal hemoglobin, and review of the literature

Purpose: A program of cord blood stem cell (CBSC) transplants for patients with β-thalassemia major was initiated in conjunction with the prenatal diagnostic service in 1994. Two patients who received HLA-matched related CBSC transplants with posttransplant fetal hemoglobin (HbF) expression are described and the literature is reviewed. Patients and Methods: After screening 12 pregnancies, matched sibling CBSC transplants were performed for 2 girls with β-thalassemia major when they were 3.8 and 2.2 years old, respectively. Their HbF was assayed serially. Results: The nucleated cell counts/kg were 11.4 x 10 7 and 6.2 x 10 7 , which engrafted on days 19 and 24, respectively. The children are now transfusion-independent at 3 years and 1.2 years posttransplant. Their HbF levels showed a rapid rise posttransplant and reached peak levels of 37.2% and 42.2% on day 83 and day 88, respectively. The HbF levels declined to 1.0% and 3.8% on day 581 and day 305, respectively. Nine other sibling CBSC transplants for thalassemias have been reported with an engraftment rate of approximately 50%. Graft rejection was related to insufficient CBSC number in one. Conclusions: HbF levels in patients with β-thalassemia major after CBSC transplants could be influenced by many factors, including reactivation of HbF synthesis, intrinsic rate of Hb switching of CBSC, and mixed chimerism.