Congenital fibrinogen disorder caused by digenic mutations of the FGA and FGB genes.

Objectives: Congenital fibrinogen disorders (CFDs) are caused by monoallelic or biallelic mutations in FGA, FGB, and FGG genes. Quantitative CFDs include afibrinogenemia and hypofibrinogenemia, while qualitative CFDs consist of dysfibrinogenemia and hypodysfibrinogenemia. Hypofibrinogenemia and dysfibrinogenemia are autosomal dominant disorders while afibrinogenemia is a recessive one. We aimed to perform genetic diagnosis of a Chinese patient with CFD.Methods: DNA was extracted from peripheral blood mononuclear cells (PBMCs) and targeted next generation sequencing (NGS) was applied using amplicon-based panel (www.ampliseq.com) targeting all exons and splice sites of FGA, FGB, and FGG genes. Identified mutations were confirmed by Sanger sequencing.Results: We have identified a novel heterozygous FGB c.560_561delTG (p.Val187GlufsTer2) frameshift deletion and a novel heterozygous FGA c.190T > G (p.Cys64Gly) missense mutations in a Chinese patient with CFD.Conclusion: This is the first report of digenic variants causing CFD, and these findings may improve understanding of the genetic architecture of CFD.