Case Report: The third-generation sequencing confirmed a novel 7.2 Kb deletion at β-globin gene in a patient with rare β-thalassemia

Abstract

Background: Thalassemia was the most common monogenic diseases worldwide, which was caused by mutations, deletions or duplications in human globin genes which disturbed the synthesis balance between α- and β-globin chains of hemoglobin. There were many classics methods to diagnose thalassemia, but all of them had limitations. Although variations in the human β-globin gene cluster were mainly point mutations, novel large deletions had been described in recent years along with the development of DNA sequencing technology.Case report: We present a case of 32-year-old male with abnormal hematological results. However, 23 genotypes of the most common thalassemia were not detected by two independent conventional platforms. Finally, using multiplex ligation-dependent probe amplification (MLPA), third-generation sequencing (TGS) and Gap PCR detection methods, we first confirmed the case with a novel 7.2 Kb deletion (Chr11:5222800-5230034, hg38) located at HBB gene.Conclusion: Our results showed that TGS technology was a powerful tool for thalassemia breakpoint detection, had promising potentiality in genetic screening of novel thalassemia, especially for the novel deletions in globin genes.

Utilization of multiple genetic methods for prenatal diagnosis of rare thalassemia variants

“…According to the phenotype of the proband and that of those two deletional β-thalassemia carriers, the deletion may cause β 0 thalassemia. Interestingly, the result of MLPA for the novel 7.2 kb deletion was the same as the one we had described ( Zhong et al, 2022 ). It has been shown that SMRT sequencing played an important role in thalassemia breakpoint detection.…”

“…There were AT-rich stretches around the 3′breakpoint, which may be significant in the recombination. A similar situation was observed in Taiwanese β-thalassemia and the case with a novel 7.2 kb deletion (Chr11:5222800-5230034, hg38) located in the HBB gene ( Zhong et al, 2022 ). According to the phenotype of the proband and that of those two deletional β-thalassemia carriers, the deletion may cause β 0 thalassemia.…”

Third generation sequencing transforms the way of the screening and diagnosis of thalassemia: a mini-review

“…This is due to the significant advantage of TGS in read length, which is much longer than that of NGS, making it easier to detect deletion variants in thalassemia genes ( 23 ). Medical practitioners have started to recognize TGS as the preferred method over NGS for detecting long deletion variants in the thalassemia gene ( Table 1 ) ( 23 , 27 , 28 , 30 , 31 , 33 ). On the other hand, NGS faces difficulties in accurately sequencing regions with abnormal GC content and highly repetitive sequences, which can lead to missed mutations and false-negative results.…”