This study is looking at a special treatment called **HLA-haploidentical stem cell transplantation** for people with severe **sickle cell disease**. Sickle cell disease is a blood disorder where red blood cells become misshapen and cause health problems. The treatment involves replacing these problematic cells with healthy ones from a family member who is a partial match, known as an **HLA-haploidentical donor**.

Before the transplant, patients will receive low-dose **total body irradiation (TBI)** and medications like **fludarabine and cyclophosphamide** to prepare their bodies. The main goal is to see if the new cells "take hold" or **engraft** by day 60 after the transplant.

• Study involves multiple hospital visits and treatments over several weeks.
• Participants must be 16-60 years old and have a related donor.
• Potential risks include reactions to the treatment and complications from the transplant.

This study aims to help those with serious complications from sickle cell disease, like frequent pain episodes or other severe conditions. Participants must meet specific health requirements and agree to the process, including informed consent.