Hydroxyurea therapy for diverse pediatric populations with sickle cell disease.

Hydroxyurea (HU) is the first widely used treatment to have an impact on the severity of disease in adult patients with sickle cell anemia, but limited data are available for younger patients or those with variant genotypes. We reviewed 324 months of experience with HU in 16 patients from 5.3 to 18.4 years of age treated for 6 to 50 months. The major toxicity was reversible neutropenia. Linear growth continued unchanged, and all patients gained weight. Hematologic results were similar to those reported in adults with increases in mean corpuscular volume (MCV) and total and fetal hemoglobin (HbF). We noted that the maximal hematologic effects occurred at less than the maximum dose. Clinically, patients experienced an 80% reduction in episodes of acute chest syndrome and a reduced need for blood transfusion, as well as a 30% decrease in the number of hospitalizations for painful events during HU therapy compared with an equivalent number of months before HU. These highly statistically significant results confirmed the value of HU in ameliorating the severe clinical course of pediatric patients. Similar effects were observed in three patients with sickle beta degrees-thalassemia, sickle beta+-thalassemia, and S-O Arab. Recurrent acute splenic sequestration and progressive symptomatic osteonecrosis were observed during HU. Thus, HU may not prevent the development of complications once organ damage is present. The challenge remains to determine when and to which pediatric patients with sickle cell disease HU should be offered.