Hydroxyurea in sickle cell disease—A study of clinico-pharmacological efficacy in the Indian haplotype

There is clinical variability in the presentation of sickle cell disease among Indians. Vaso-occlusive crisis is common among non-tribal patients. Hydroxyurea, induces fetal hemoglobin (HbF) synthesis and reduces the clinical severity of sickle cell disease but individual patients have a variable response. This study was undertaken to investigate the efficacy and safety of hydroxyurea in Indians with severe manifestations where the βs gene is linked to the Arab–Indian haplotype and is associated with higher HbF levels. Seventy-seven patients (29 adult sickle homozygous, 25 pediatric sickle homozygous, 23 adult sickle β-thalassemia) selected for hydroxyurea therapy were evaluated for clinical, hematological, biochemical and genetic parameters and were followed for 24 months. Ninety-eight point seven percent of the sickle chromosomes were linked to the Arab–Indian haplotype, 27% of patients had associated α thalassemia and 65% were Xmn I +/+. Seventy-eight percent of the patients had no further crises after starting hydroxyurea. This effect was accompanied by a significant increase in HbF (p < 0.001), but this increase was variable in individual cases. There was also an increase in γ gene mRNA expression in the few cases so studied. Hemoglobin levels increased significantly (p < 0.001) resulting in the cessation of blood transfusions. Leucopoenia was observed in one patient. Hydroxyurea was effective in reducing the clinical severity in Indian patients who initially had higher HbF levels and the presence of ameliorating factors, such as α-thalassemia and the Xmn I polymorphism. Hydroxyurea therapy with careful monitoring can thus change the quality of life of Indians with sickle cell disease.