Mutations on theα2-Globin Gene That May Triggerα+-Thalassemia

Molecular basis of α-thalassemia

α-Thalassemia is an inherited, autosomal recessive, disorder characterized by a microcytic hypochromic anemia. It is one of the most common monogenic gene disorders in the world population. The clinical severity varies from almost asymptomatic, to mild microcytic hypochromic, and to a lethal hemolytic condition, called Hb Bart's Hydrops Foetalis Syndrome. The molecular basis are usually deletions and less frequently, point mutations affecting the expression of one or more of the duplicated α-genes. The clinical variation and increase in disease severity is directly related to the decreased expression of one, two, three or four copies of the α-globin genes. Deletions and point mutations in the α-globin genes and their regulatory elements have been studied extensively in carriers and patients and these studies have given insight into the α-globin genes are regulated. By looking at naturally occurring deletions and point mutations, our knowledge of globin-gene regulation and expression will continue to increase and will lead to new targets of therapy.

Hb Dapu (HBA2: c.52G > T): A Novel Nondeletional α-Thalassemia Mutation

We report a novel mutation on the α2-globin gene, Hb Dapu [α17(A15)Val →Phe (α2); HBA2: c.52G > T] detected in a Chinese family. This mutation gives rise to a previously undescribed hemoglobin (Hb) variant that was undetectable by electrophoretic or chromatographic methods. The combination of this mutation with an in cis deletion of a double α-globin gene resulting in a mild form of Hb H (β4) disease, is consistent with a thalassemic phenotype associated with the novel mutation.