Repeat Peripheral Blood Stem Cell Transplantation for Patients With Sickle Cell Disease and Falling Donor Myeloid Chimerism Levels

This study offers a repeat stem cell transplant (using peripheral blood stem cells) for patients with Sickle Cell Disease (SCD) or beta thalassemia who previously received a stem cell transplant but are now showing signs that the disease is returning. This can happen when the donor's cells are being gradually replaced by the patient's own diseased cells — a situation called falling donor chimerism. A successful stem cell transplant can effectively cure sickle cell disease and thalassemia, but sometimes the donor cells don't fully take hold long-term. When disease symptoms return, a second transplant from the same related donor may restore the benefit. This study tests whether this 'boost' transplant is safe and effective. **You may be eligible if...** - You have a history of SCD or beta thalassemia and previously had an allogeneic stem cell transplant - Your disease has recurred with clinical symptoms (e.g., painful crises, anemia, transfusion dependence) - You are 4 years of age or older - Your heart ejection fraction is at least 35% - Your lung function (DLCO) is at least 35% - Your related donor from the original transplant is willing and eligible to donate again **You may NOT be eligible if...** - You have a very poor performance status (ECOG 3 or higher) - You have an active uncontrolled infection - You are pregnant or breastfeeding - You have had a secondary cancer (other than skin cancer) - You have strong antibodies against the donor's tissue type (HLA) **Talk to your doctor** about your transplant history, current disease status, and whether your original donor is available and suitable for a repeat donation.