Fetal hemoglobin regulation in β-thalassemia: heterogeneity, modifiers and therapeutic approaches.

INTRODUCTION: Stress erythropoiesis induces fetal hemoglobin (HbF) expression in β-thalassemias, however the level of expression is highly variable. The last decade has seen dramatic advances in our understanding of the molecular regulators of HbF production and the genetic factors associated with HbF levels, leading to the promise of new methods of the clinical induction of HbF. Areas covered: This article will review the heterogeneity and genetic modifiers of HbF and HbF induction therapy in β-thalassemia. Expert commentary: One promising curative β-thalassemia therapy is to induce HbF synthesis in β-thalassemic erythrocytes to therapeutic levels before clinical symptom occurs. Further understanding of HbF level variation and regulation is needed in order to predict the response from HbF-inducing approaches.