Gγ-Xmn I polymorphism: a significant determinant of β-thalassemia treatment without blood transfusion.

β-thalassemia is characterized by impaired β-chain synthesis leading to ineffective erythropoiesis, severe anemia, and a need for blood transfusion. Presence of Xmn I polymorphism (-158 C-T nucleotide change) in γ-globin gene is associated with a higher fetal hemoglobin and a lesser clinical severity. This prospective study attempted to find out the effect of hydroxyurea (HU) on β-thalassemia patients in the presence or absence of Xmn I polymorphism. A total of 143 consecutive β-thalassemia patients received HU (16 mg/kg/d). Sixty-four (44.7%) had Xmn I polymorphism (either homozygous or heterozygous). Patients were evaluated at a median duration of 3 years (range, 6 mo to 9 y). Responders became transfusion independent after 6 months, partial responders had a least 50% reduction in transfusion requirement and nonresponders had no significant reduction. Of the 64 patients with Xmn I polymorphism, 44 (69%) showed response (P<0.01), whereas in those who lacked Xmn I polymorphism (n=79), only 17 (21%) were responders. This study showed that the presence of Xmn I polymorphism in β-thalassemia is a predictor of response to HU and highlights the possibility of managing this subset of patients without blood transfusion.