[Two HLA-loci mismatched sibling cord blood transplantation in a severe beta-thalassemia patient].

ABSTRACT

Allogeneic hematopoietic stem cell transplantation is the only curative therapy for severe beta-thalassemia. This time, the experience of utilizing HLA 2-loci mismatched sibling cord blood transplantation (CBT) in a child with severe beta-thalassemia was firstly reported in our country. A 3-year-male patient had been diagnosed with severe beta-thalassemia at 6 months of age (HbF 86.6%, HbA1 1.7%, HbA2 1.7%, beta globin gene mutation CD17, A-->T/IVS-II-654, C-->T). The patient's HLA typing was A 24,11, B 58,35 and DRB1 03,15. During a subsequent maternal pregnancy. The prenatal diagnosis for thalassemia and prenatal HLA typing analysis were performed on 18 weeks of pregnancy. The results indicated that the male fetus was a heterozygote (beta globin gene mutation N/CD17, A-->T), HLA typing was A 24,11, B 58,51 and DRB1 03,12. 120 ml cord blood was collected at time of delivery, the total numbers of nucleated cells, CFU-GM and CD34(+) cells were 1.830 x 10(9), 16.653 x 10(5) and 3.11 x 10(6), respectively. A new conditioning regimen including hypertransfusion, continuous i.v. desferrioxamine, busulfan, cyclophosphamide, antithymocyte globulin plus hydroxyurea and fludarabine. GVHD prophylaxis comprised cyclosporin A and mycophenolate mofetil. The viability of cord blood at the time infusion was 92%, The total numbers of nucleated cells, CFU-GM and CD34(+) cells in the transfused cord blood were 12.06 x 10(7)/kg, 1.098 x 10(5)/kg, and 2.04 x 10(6)/kg, respectively. Results showed that the patient's clinical course after cord blood transplantation was unremarkable. Acute GVHD grade I developed on day 15, methylprednisolone 2 mg/kg was given to cure. Neutrophil engraftment (ANC > 0.5 x 10(9)/L) on day 17, platelet engraftment (> 50 x 10(9)/L) on day 50. The patients became independent from red blood cell transfusion since day 80 (when his hemoglobin level kept > 12.5 g/L). His beta globin gene mutation and HLA typing were all the same as the donor's analyzed on day 60 and 200. There was also a switch in blood group from A pre-transplant to O post-transplant. It is concluded that the new conditioning and GVHD prophylaxis regimens allow a successful engraftment in this case. This observation may contribute in developing UCBT as an alternative when matched sibling donors are not available.