Congenital (hypo-)dysfibrinogenemia and bleeding: A systematic literature review

Ranging from bleeding to thrombosis, the clinical features of congenital fibrinogen qualitative disorders, including dysfibrinogenemia and hypodysfibrinogenemia, are highly heterogeneous. Although the associations between some specific fibrinogen mutations and the thrombotic phenotypes have been well elucidated, the underlying mechanism between fibrinogen variants and bleeding events remains underestimated. After systematically reviewing the literature of (hypo-)dysfibrinogenemia patients with bleeding phenotypes, we identified several well-characterized bleeding-related fibrinogen variants in those patients. Several possible pathomechanisms are proposed to explain the genotype-phenotype associations: 1, mutations in the NH₂-terminal portion of the Aα chain hamper fibrinogen fitting into the active site cleft of thrombin and drastically slow the conversion of fibrinogen into monomeric fibrin; 2, mutations adding new N-linked glycosylation sites introduce bulky and negatively charged carbohydrate side chains and undermine the alignment of fibrin monomers during polymerization; 3, mutations generating unpaired cysteine form extra disulfide bonds between the abnormal fibrinogen chains and produce highly branched and fragile fibrin networks; 4, truncation mutations in the fibrinogen αC regions impair the lateral fibril aggregation, as well as factor XIII crosslinking, endothelial cell and platelet binding. These established relationships between specific variants and the bleeding tendency will help manage (hypo-)dysfibrinogenemia patients to avoid adverse bleeding outcomes.