LabMed

Delta-Thalassemia

At a Glance

Isolated delta-thalassemia usually has no clinical manifestations. However, it may be associated with beta-thalassemia.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

In a patient with microcytic anemia, if iron deficiency anemia is ruled out and red blood cell (RBC) indices suggest beta-thalassemia, then HPLC is performed on lysed RBCs to measure hemoglobin A22delta2) concentration and hemoglobin F (α2gamma2) concentration. As these 2 forms of hemoglobin do not utilize beta chains, they are elevated in beta-thalassemia but not in alpha-thalassemia. However, if there is a concomitant delta-thalassemia, as well as the beta-thalassemia, then hemoglobin A2 will be low to normal in the heterozygous state (delta+-thalassemia) or absent in the homozygous state (delta0-thalassemia). Therefore, the HPLC results (low to normal hemoglobin A2 and elevated hemoglobin F) will be similar to those of hereditary persistence of fetal hemoglobin (HPFH) or a delta-beta-thalassemia due to a large deletion.

The isolated increase in hemoglobin F due to concomitant beta-thalassemia and delta-thalassemia can be distinguished from increased hemoglobin F due to Hereditary Persistence of Fetal Hemoglobin (HPFH) by the distribution of hemoglobin F in red cells. In beta-thalassemias, the hemoglobin F is heterogenous in expression in erythrocytes, whereas, in HPFH, the hemoglobin F is distributed uniformly among the erythrocytes. The distribution of hemoglobin F can be measured by the Kleihauer-Betke acid elution test or by flow cytometry with a fluorescence labeled anti-hemoglobin F antibody.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

The Corfu mutation is a phenocopy of delta-beta-thalassemia in which a deletion of the delta chain gene coexists with a point mutation in the beta chain gene.

What Lab Results Are Absolutely Confirmatory?

Identification of the mutation in the delta chain gene is absolutely confirmatory. Several mutations are common, such as the δ+27C→T mutation, which is common in the Mediterranean region.

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