Thalassemia is an inherited blood disorder imposing a significant social and economic burden. Comprehensive screening strategies are essential for the prevention and management of this disease. Third-generation sequencing (TGS), a breakthrough technology, has shown great potential for screening and diagnostic applications in various diseases, while its application in thalassemia detection is still in its infancy. This review aims to understand the latest and most widespread uses, advantages of TGS technologies, as well as the challenges and solutions associated with their incorporation into routine screening and diagnosis of thalassemia. Overall, TGS has exhibited higher rates of positive detection and diagnostic accuracy compared to conventional methods and next-generation sequencing technologies, indicating that TGS will be a feasible option for clinical laboratories conducting in-house thalassemia testing. The implementation of TGS technology in thalassemia diagnosis will facilitate the development of effective prevention and management strategies, thereby reducing the burden of this disease on individuals and society.

Targeted long-read sequencing (LRS) is expected to comprehensively analyse diverse complex variants in haemophilia A (HA) and B (HB), caused by the F8 and F9 genes, respectively. However, its clinical applicability still requires extensive validation. To evaluate the clinical applicability of targeted LRS-based analysis, compared with routine PCR-based methods. Gene variants of retrieved subjects were retrospectively and prospectively analysed. Whole-genome sequencing (WGS) was performed to further analyse undiagnosed cases. Breakpoints of novel genomic rearrangements were mapped and validated using long-distance-PCR and long-range-PCR combined with sequencing. Totally, 122 subjects were retrieved. In retrospective analysis of the 90 HA cases, HA-LRS assay showed consistent results in 84 cases compared with routine methods, and characterized six large deletions with their exact breakpoints confirmed by further validation in six cases (routine methods only presented failure in amplifying the involved exons). In prospective analysis of the 21 HA subjects, 20 variants of F8 were identified in 20 cases. For the remaining HA patient, no duplication/deletion or SNV/InDel was found, but a potential recombination involving exons 14 and 21 of F8 was observed by LRS. WGS analysis and further verification defined a 30,478bp tandem repeat involving exons 14-21 of F8. Among the 11 HB patients, HB-LRS analysis detected 11 SNVs/InDels in F9, consistent with routine methods. Targeted LRS-based analysis is efficient and comprehensive to identify SNVs/InDels and genomic rearrangements of haemophilia genes, especially we first expanding the panel including F9. However, further investigation for complex gross rearrangement is still essential.

Deletion or duplication in the DMD gene is one of the most common causes of Duchenne and Becker muscular dystrophy (DMD/BMD). However, the pathogenicity of complex rearrangements involving DMD, especially segmental duplications with unknown breakpoints, is not well understood. This study aimed to evaluate the structure, pattern, and potential impact of rearrangements involving DMD duplication. Two families with DMD segmental duplications exhibiting phenotypical differences were recruited. Optical genome mapping (OGM) was used to explore the cryptic pattern of the rearrangements. Breakpoints were validated using long-range polymerase chain reaction combined with next-generation sequencing and Sanger sequencing. A multi-copy duplication involving exons 64–79 of DMD was identified in Family A without obvious clinical symptoms. Family B exhibited typical DMD neuromuscular manifestations and presented a duplication involving exons 10–13 of DMD. The rearrangement in Family A involved complex in-cis tandem repeats shown by OGM but retained a complete copy (reading frame) of DMD inferred from breakpoint validation. A reversed insertion with a segmental repeat was identified in Family B by OGM, which was predicted to disrupt the normal structure and reading frame of DMD after confirming the breakpoints. Validating breakpoint and rearrangement pattern is crucial for the functional annotation and pathogenic classification of genomic structural variations. OGM provides valuable insights into etiological analysis of DMD/BMD and enhances our understanding for cryptic effects of complex rearrangements.

Thoracic aortic aneurysm/dissection (TAAD) and patent ductus arteriosus (PDA) are serious autosomal-dominant diseases affecting the cardiovascular system. They are mainly caused by variants in the MYH11 gene, which encodes the heavy chain of myosin 11. The aim of this study was to evaluate the genotype–phenotype correlation of MYH11 from a distinctive perspective based on a pair of monozygotic twins. The detailed phenotypic characteristics of the monozygotic twins from the early fetal stage to the infancy stage were traced and compared with each other and with those of previously documented cases. Whole-exome and Sanger sequencing techniques were used to identify and validate the candidate variants, facilitating the analysis of the genotype–phenotype correlation of MYH11. The monozygotic twins were premature and presented with PDA, pulmonary hypoplasia, and pulmonary hypertension. The proband developed heart and brain abnormalities during the fetal stage and died at 18 days after birth, whereas his sibling was discharged after being cured and developed normally post follow-up. A novel variant c.766 A > G p. (Ile256Val) in MYH11 (NM_002474.2) was identified in the monozygotic twins and classified as a likely pathogenic variant according to the American College of Medical Genetics/Association for Molecular Pathology guidelines. Reviewing the reported cases (n = 102) showed that the penetrance of MYH11 was 82.35%, and the most common feature was TAAD (41.18%), followed by PDA (22.55%), compound TAAD and PDA (9.80%), and other vascular abnormalities (8.82%). The constituent ratios of null variants among the cases with TAAD (8.60%), PDA (43.8%), or compound TAAD and PDA (28.6%) were significantly different (P = 0.01). Further pairwise comparison of the ratios among these groups showed that there were significant differences between the TAAD and PDA groups (P = 0.006). This study expands the mutational spectrum of MYH11 and provides new insights into the genotype–phenotype correlation of MYH11 based on the monozygotic twins with variable clinical features and outcomes, indicating that cryptic modifiers and complex mechanisms beside the genetic variants may be involved in the condition.