A Phase II Pilot Study of Nonmyeloablative Conditioning Hematopoietic Stem Cell Transplantation in Children with Sickle Cell Disease who have a Matched Related Major ABO-Incompatible Donor (Sickle-MAID).

Inclusion criteria:

Age: Patients must be ≥ 12 months and < 19 years of age at the time of study enrollment.

Diagnosis: Patients must have sickle cell disease as defined by hemoglobin electropheresis, as follows:
• homozygous Hb S disease (HbSS),
• sickle-Hb C disease (HbSC),
• sickle beta-plus-thalassemia (HbS/β+), or
• sickle beta-null-thalassemia (HbS/βo)

Eligibility for HSCT: Patients must meet standard eligibility criteria to undergo HSCT, including but not limited to one or more of the following:
• history of repeated painful episodes (more than 1) including but not limited to bony crisis. Pain may occur in typical sites associated with vaso-occlusive painful events and cannot be explained by causes other than vaso-occlusion mediated by sickle cell disease.
• history of stroke
• elevated transcranial Doppler velocity not eligible for hydroxyurea, as per TWiTCH trial (ie. severe vasculopathy)
• history of acute chest crisis or splenic sequestration crisis
• history of priapism in males
• history of osteonecrosis
• pulmonary hypertension as documented by tricuspid regurgitation jet velocity (TRV) > 2.5 m/s on echocardiogram
• red cell allo-immunization (≥ 2 antibodies) during long term transfusion therapy

Sickle complications should be present despite the use of hydroxyurea, but this is not an absolute requirement, if the treating team considers the patient to be at high risk for further crisis episodes.