Physiologic decline in fetal hemoglobin parameters in infants with sickle cell disease: Implications for pharmacological intervention

Purpose: Fetal hemoglobin (HbF) is an important determinant in the clinical severity of patients with sickle cell disease. The physiologic decline in HbF parameters in a cohort of infants with sickle cell disease was investig ated. Patients and Methods: The percent HbF and F cells were quantitated, and the HbF per F cell was then calculated. One hundred thirty-eight blood samples from 44 infants with homozygous sickle cell anemia (HbSS) and 56 samples f rom 24 infants with sickle cell hemoglobin (HbSC) were studied. Results: Infants with HbSS had a logarithmic decline in HbF parameters; at 24 months, the average HbF was 14.6% +/- 7.3% and the % F cells was 64.7% /- 16.9%. The amount of HbF in each F cell (HbF per F cell) was <15 pg/cell , a suggested threshold for intracellular sickle polymerization, by age 12 months. Infants with HbSC had a more rapid decline: at 12 months the averag e % HbF was 12.2% +/- 9.3%, the % F cells was 60.5% +/- 18.7%, and the HbF per F cell was <10 pg/cell. Conclusions: By age 2 years, HbF parameters including the % HbF, % F cells, and the HbF per F cell decrease to levels insufficient to inhibit sickling . Pharmacologic intervention designed to enhance HbF production and prevent chronic organ damage should be considered during infancy.