FGB and Hypofibrinogenemia: Congenital hypofibrinogenemia can be caused by mutations in FGA, FGB, or FGG. However, only 6 mutations (listed in Table 1, with predicted sequences) in the FGG sequence encoding the fibrinogen γ chain residues between 310 and 401 (including signal peptide) are known to cause hypofibrinogenemia and hepatocyte ER storage of abnormal fibrinogen [2–13].