Case report: A novel 10.8-kb deletion identified in the beta-globin gene through the long-read sequencing technology in a Chinese family with abnormal hemoglobin testing results

Background: Thalassemia is a common inherited hemoglobin disorder caused by a deficiency of one or more globin subunits. Substitution variants and deletions in the HBB gene are the major causes of b-thalassemia, of which large fragment deletions are rare and difficult to be detected by conventional polymerase chain reaction (PCR)-based methods. Case report: In this study, we reported a 26-year-old Han Chinese man, whose routine blood parameters were found to be abnormal. Hemoglobin testing was performed on the proband and his family members, of whom only the proband's mother had normal parameters. The comprehensive analysis of thalassemia alleles (CATSA, a long-read sequencing-based approach) was performed to identify the causative variants. We finally found a novel 10.8-kb deletion including the b-globin (HBB) gene (Chr11:5216601-5227407, GRch38/hg38) of the proband and his father and brother, which were consistent with their hemoglobin testing results. The copy number and exact breakpoints of the deletion were confirmed by multiplex ligation-dependent probe amplification (MLPA) and gap-polymerase chain reaction (Gap-PCR) as well as Sanger sequencing, respectively. Conclusion: With this novel large deletion found in the HBB gene in China, we expand the genotype spectrum of b-thalassemia and show the advantages of long-read sequencing (LRS) for comprehensive and precise detection of thalassemia variants.

Automated summary

By performing comprehensive hemoglobin testing and genetic analysis on a 26-year-old Han Chinese man, it was found that he and his father and brother had a rare 10.8-kb large deletion of the b-globin (HBB) gene. The copy number and exact breakpoints of the deletion were confirmed using MLPA, Gap-PCR, and Sanger sequencing. This study expands the genotype spectrum of b-thalassemia in China and demonstrates the advantages of long-read sequencing (LRS) for comprehensive and precise detection of thalassemia variants.