A novel 15.8 kb deletion α-thalassemia confirmed by long-read single-molecule real-time sequencing: Hematological phenotypes and molecular characterization

Background: Thalassemia is the most frequent recessive Mendelian inherited monogenic disease worldwide, and is characterized by the impaired synthesis of globin chains due to disease-causing variants in alpha- or beta-globin genes. There are many conventional methods to diagnose thalassemia but all of them have limitations. Case report: We present the case of a 37-year-old female with abnormal values of routine hematological indices who was admitted for genetic screening of thalassemia. Genomic DNA was extracted and used for genetic assays covering the known and potential novel genotypes in HBA and HBB genes using a suspension-array system, gap-polymerase chain reaction (Gap-PCR), PCR-reverse dot blot (PCR-RDB) and multiplex ligation-dependent probe amplification (MLPA). Finally, using long-read single-molecule real-time (SMRT) sequencing, we first confirmed the case with a novel 15.8 kb deletion located in the HBA gene (Chr16:163886-179768, GRch38/hg38). Conclusions: Our results showed that long-read SMRT sequencing has great advantages in the detection of rare alpha-globin gene variants. This study may provide a reference protocol for the use of long-read SMRT sequencing for the detection of known and potential novel genotypes of thalassemia in the population and improve the accuracy of genetic counseling and prenatal diagnosis.