Deltaglobin

Deltaglobin is the delta globin polypeptide, one of the globin chains that form adult hemoglobin. It is encoded by the HBD gene on chromosome 11 and is a component of hemoglobin A2 (HbA2), which in healthy adults typically makes up about 2–3% of total hemoglobin. HbA2 consists of two alpha chains and two delta chains (α2δ2).

Delta-globin belongs to the beta-like globin gene family and is expressed in erythroid cells. Its production begins in late fetal life and continues at lower levels in adulthood. The delta chain is similar in structure to other beta-like globin chains but is present in much smaller amounts than the main adult beta-globin chain.

Regulation of deltaglobin expression is part of the broader developmental switch that controls globin gene expression. While fetal development relies predominantly on gamma-globin, the delta-globin gene is activated to yield HbA2 in adults. The precise regulation ensures that HbA2 remains a minor but stable portion of adult hemoglobin.

Clinical significance of delta-globin relates mainly to genetic disorders affecting the HBD gene. Delta-thalassemia, caused by reduced or absent delta-globin production, lowers HbA2 levels. Because HbA2 is used diagnostically—particularly in evaluating suspected beta-thalassemia trait—characteristic changes in HbA2 can influence interpretation. Variants in HBD can also alter delta-globin function or its detection by laboratory methods such as electrophoresis or high-performance liquid chromatography.

In summary, deltaglobin is the delta chain of HbA2, encoded by HBD, contributing to a small but important fraction of adult hemoglobin and to the clinical landscape of globin gene disorders.