Precise Reproductive Counseling Enabled by Long-Read Sequencing in a Case of a F8 Intron 1 Inversion and Duplication

To demonstrate the clinical value of integrating next-generation sequencing (NGS) with long-read sequencing (LRS) for resolving complex F8 variants and guiding personalized reproductive strategies in Haemophilia A (HA).

A patient with a history of three adverse pregnancy outcomes underwent comprehensive preconception genetic evaluation. NGS-based carrier screening initially excluded common single-gene disorders but flagged complex variants in the F8 gene. Subsequent LRS was employed to characterize the specific structural variations.

NGS screening excluded 155 single-gene disorders and normal FMR1 repeats. LRS confirmed F8 intron 1 inversion (Inv1) and a duplication variant, while ruling out intron 22 inversion. The patient was identified as an asymptomatic female carrier. Based on this diagnosis, reproductive counseling recommended spouse testing, preimplantation genetic testing for monogenic diseases (PGT-M) combined with aneuploidy screening (PGT-A), and prenatal diagnosis.

This case underscores that while NGS is an effective screening tool, its limitations in detecting structural variations necessitate a stepwise diagnostic approach. Integrating LRS was indispensable for resolving complex F8 variants, transforming ambiguous genetic signals into precise diagnoses. This precision serves as the cornerstone for accurate risk assessment and empowers couples with informed reproductive options, exemplifying a "personalized reproductive blueprint".