Congenital hypofibrinogenaemia is a quantitative fibrinogen disorder characterized by proportionally decreased levels of functional and antigenic fibrinogen. Mutations accounting for quantitative fibrinogen disorders are relatively frequent in the conserved COOH-terminal globular domains of the γ and Bβ chains. The latter mutations are of particular interest since the Bβ-chain is considered the rate-limiting chain in the hepatic production of the fibrinogen hexamer.