Deltathalassemia

Deltathalassemia is a rare genetic blood disorder characterized by a reduced or absent production of the delta-globin chain, a component of hemoglobin. Hemoglobin is the protein in red blood cells responsible for carrying oxygen. While alpha and beta-globin chains are the primary components of adult hemoglobin (hemoglobin A), delta-globin chains are normally produced in small amounts and are a component of hemoglobin A2.

The genetic basis of deltathalassemia lies in mutations within the HBD gene, which encodes the delta-globin chain. These mutations can lead to a complete absence (null allele) or a significant reduction in delta-globin production. Because delta-globin is a minor component of hemoglobin, the absence of delta-globin chains typically has a minimal or no observable clinical effect on its own. Individuals with isolated deltathalassemia are usually asymptomatic.

However, deltathalassemia is often identified incidentally during newborn screening for other hemoglobinopathies or when investigating the presence of hemoglobin A2. In some cases, the genetic defect affecting the delta-globin gene may be linked to or occur in conjunction with mutations affecting the beta-globin gene, which can lead to beta-thalassemia. In such compound heterozygotes, the clinical presentation is primarily determined by the severity of the beta-thalassemia. Diagnosis is typically made through hemoglobin electrophoresis, which reveals a decreased or absent hemoglobin A2. Genetic testing can confirm the specific mutations in the HBD gene. Treatment is generally not required for isolated deltathalassemia, as it is considered clinically benign.