Abstract
Congenital fibrinogen disorders are classified into two types of plasma fibrinogen
defects: type I (quantitative fibrinogen deficiencies), that is, hypofibrinogenemia
or afibrinogenemia, in which there are low or absent plasma fibrinogen antigen levels,
respectively, and type II (qualitative fibrinogen deficiencies), that is, dysfibrinogenemia
or hypodysfibrinogenemia, in which there are normal or reduced antigen levels associated
with disproportionately low functional activity. These disorders are caused by mutations
in the three fibrinogen-encoding genes FGA, FGB, and FGG. Afibrinogenemia is associated with mild to severe bleeding, whereas hypofibrinogenemia
is often asymptomatic. For these quantitative disorders, the majority of mutations
prevent protein production. However, in some cases, missense or late-truncating nonsense
mutations allow synthesis of the mutant fibrinogen chain, but intracellular fibrinogen
assembly and/or secretion are impaired. Qualitative fibrinogen disorders are associated
with bleeding, thrombosis, or both thrombosis and bleeding, but many dysfibrinogenemias
are asymptomatic. The majority of cases are caused by heterozygous missense mutations.
Here, we review the laboratory and genetic diagnosis of fibrinogen gene anomalies
with an updated discussion of causative mutations identified.
Keywords
congenital fibrinogen disorders - mutations - afibrinogenemia - hypofibrinogenemia
- dysfibrinogenemia - hypodysfibrinogenemia - bleeding - thrombosis