Hematopoietic stem cell transplantation is currently the only way to cure thalassemia, one of its main obstacles is the rejection after transplantation, chimerism continued to decline, which eventually lead to transplant failure. chimerism is a key indicator of the succession of immune response, which is a key indicator for predicting the failure of hematopoietic stem cell transplantation and provides an important basis for early detection of rejection. Transplantation of continuous chimerism can detect early unstable chimeras and rejection.The chimerism rates after transplantation were continuously monitored using fluorescence labeled multiplex PCR amplification of short tandem repeats (STR-PCR)

,and then follow our STR different rates for early interventional therapy to prevent further reduction in chimerism leading to lead to graft failure.

Inclusion Criteria:

1. Diagnosis of thalassemia major
2. There is no restriction on age or gender.
3. Underwent allogeneic hematopoietic stem cell transplantation, including sibling transplantation, unrelated transplantation and haploidentical transplantation.
4. On +45 day after transplantation, check patients with STR less than 80%.
5. Patients underwent reduce of dosage with a failure treatment by
6. Body condition score (ECOG score) is less than or equal to 1 point who meet follow-up conditions.

Exclusion Criteria:

Complicated with severe cardiac insufficiency and cardiac ejection fraction (EF) was lower than 50%. Complicated with severe pulmonary insufficiency (obstructive and / or restrictive ventilatory disorders). Complicated with severe liver function damage and liver function index (ALT or TBIL) is more than 2 times of the upper limit of the normal value. Complicated with severe renal dysfunction and renal function index (Cr or BUN) is 2 times of the upper limit of the normal value. Complicated with severe active bleeding