Recent advances in the molecular understanding of non-transfusion-dependent thalassemia.

Thalassemias are a group of inherited autosomal recessive hematologic disorders that occur because of defects in the alpha (α)- and beta (β)-globin genes of adult hemoglobin (Hb). An imbalance in the synthesis of one or more of the globin chains can result in a wide spectrum of phenotypes depending on the type and amount of globin synthesized and additional genetic modifiers. In patients with thalassemia intermedia, a condition known as non-transfusion-dependent thalassemia (NTDT), transfusion requirements are absent or episodic. Non-transfusion-dependent thalassemia includes β-thalassemia intermedia, HbE β-thalassemia, and α-thalassemia intermedia, also known as Hb H disease. This article focuses on the molecular features and genetic mutations specific to NTDT.