Exclusion Criteria
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1. Chronic transfusion therapy 2. Cancer 3. Less than 5th percentile (10th percentile for the pilot study) height, weight, or head circumference for age 4. Severe developmental delay (e.g., cerebral palsy or other mental retardation, Grade III/IV intraventricular hemorrhage) 5. Stroke with neurological deficit 6. Surgical splenectomy 7. Participating in other clinical intervention trials 8. Probable or known diagnosis of Hemoglobin S-Hereditary Persistence of Fetal Hemoglobin 9. Known hemoglobin S-beta plus thalassemia (hemoglobin A present) 10. Any condition or chronic illness, which in the opinion of the principal investigator, makes participation unadvised or unsafe 11. Inability or unwillingness to complete baseline (pre-enrollment) studies, including blood or urine specimen collection, liver-spleen scan, abdominal sonogram, neurological examination, neuropsychological testing, or transcranial Doppler ultrasound (interpretable study not required, but confirmed velocity greater than 200 cm/sec results in ineligibility) 12. Previous or current treatment with hydroxyurea (HU) or another anti-sickling drug 13. The following exclusion criteria are transient; patients can be re-evaluated for eligibility:1. Hemoglobin less than 6.0 gm/dL2. Reticulocyte count less than 80,000/cu mm if hemoglobin is less than 9 gm/dL3. Neutrophil count less than 2,000/cu mm4. Platelet count less than 130,000/cu mm5. Blood transfusion in the 2 months prior to study entry unless HbA is less than 10%6. ALT greater than twice the upper limit of normal7. Ferritin less than 10 ng/ml8. Serum creatinine greater than twice the upper limit of normal for age9. Bayley standardized mental score below 70 |