δ-Thalassemia with Complete Absence of Hb A₂ in a Chinese Family

Area of Science:

• Medical Genetics
• Hematology
• Molecular Biology

Background:

• Delta-thalassemia (δ-thal) is a genetic blood disorder.
• Hemoglobin A2 (HbA2) levels are typically used to screen for thalassemia variants.
• Coinheritance of different thalassemia types can complicate diagnosis.

Purpose of the Study:

• To characterize a Chinese family with δ-thalassemia.
• To investigate the diagnostic challenges posed by coinheritance of δ-thal and β-thalassemia (β-thal).
• To emphasize the need for careful screening in cases of coexisting thalassemia traits.

Main Methods:

• Genetic analysis of the HBD gene.
• Hemoglobin electrophoresis to determine HbA2 levels.
• Clinical and hematological assessment of family members.

Main Results:

• A daughter was found to be homozygous for δ-thal (HBD: c.-127T>C), showing complete HbA2 deficiency.
• The mother was a heterozygote with low HbA2 levels.
• The father, a β-thal heterozygote, had normal HbA2 due to coinheritance with δ-thal.

Conclusions:

• δ-thalassemia alone did not cause clinical or hematological abnormalities in this family.
• Routine screening may miss β-thalassemia when coinherited with δ-thalassemia.
• Comprehensive genetic testing is crucial for accurate diagnosis in individuals with suspected or confirmed thalassemia.