A 13-bp deletion in the 3' untranslated region of the β-globin gene causes β-thalassemia major in compound heterozygosity with IVSII-1 mutation

Objective: To describe hematological and molecular features of a 13-bp deletion in the 3' untranslated region(3' UTR) of the β-globin gene in carrier individuals and a compound heterozygous patient.

Subjects and methods: Five members of an Iranian family of Persian ethnic origin were studied. Red blood cell indices and hemoglobin analysis were carried out according to standard methods. Genomic DNA was obtained from peripheral blood cells by salting-out procedures. β-Globin gene amplification and DNA sequencing were performed.

Results: One patient had a 13-bp deletion in the 3' UTR of the β-globin gene that causes the β-thalassemia phenotype in combination with the IVSII-1 (G→A) mutation. The patient had inherited the IVSII-1 (G→A) mutation from his mother, while the second β-globin gene (inherited paternally) had a 13-bp deletion at nucleotide 90 downstream of the termination codon (CD +90 del 13 bp).The patient's father and paternal grandmother, who are carriers of this deletion, had no hematological abnormalities.

Conclusion: This case showed a patient with a 13-bp deletion in the 3' UTR of β-globin gene that could cause a slight decrease in the stability of the mRNA, but did not have a hematological effect in the heterozygotes. The 13-bp deletion could be clinically important only in situations where β-chain synthesis in trans is compromised.