Interaction between Hb E and Hb Yala (HBB:c.129delT); a novel frameshift beta globin gene mutation, resulting in Hemoglobin E/β⁰ thalassemia

ABSTRACT

Objectives: There are more than 200 known mutations found in patients with β-thalassemia, a possibility to identify an unknown or novel mutation becomes less possible. Here, we report a novel mutation in a patient from Thailand who presented with chronic hemolytic anemia.

Methods: A comprehensive hematology and DNA analysis was applied in the index patient and her mother.

Results: Hematological and hemoglobin analyses were consistent with the clinical diagnosis of Hb E/β⁰-thalassemia. However, we could find only Hb E heterozygous mutation using our common polymerase chain reaction-based mutation detection of the β-globin genes. Furthermore, the molecular analysis demonstrated a novel T-deletion at codon 42 of the second exon of the β-globin gene which we named ‘Hb Yala’ according to the origin of this index family.

Discussion: This mutation was assumed to generate a truncated β-globin chain terminating at codon 60 with possible unstable variant leading to a ‘null’ or β⁰-thalassemia. However, the clinical phenotype was surprisingly mild and no other ameliorating genetic factors, including co-inheritance of α-thalassemia and high propensity of Hb F by Xmn I polymorphism, were found.

Conclusion: This report has provided evidence that genotype–phenotype correlation in thalassemia syndromes is highly complex and a correct clinical severity classification of thalassemia should be mainly based on clinical evaluation.

KEYWORDS:

• β-Globin mutation
• hemoglobin Yala
• thalassemia
• Hb E/β-thalassemia
• hemoglobin variant
• transfusion-dependent thalassemia
• non-transfusion-dependent thalasssemia
• frameshift mutation

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Grant Chalermprakiat Funding, Faculty of Medicine Siriraj Hospital; the Royal Golden Jubilee Ph.D. Program: [(Grant Number PHD/0089/2548)].