The most frequent sites for these mutations code for the N-terminus of the Aα chain or the C-terminus of the γ chain that lead to defective assembly of fibrin in early clot formation and thereby a bleeding predisposition.[1] Two particular missense mutations represent the majority (74% in one study of 101 individuals) of all mutations associated with dysfibrinogenemia and therefore represent prime sites to examine in the initial testing of individuals having a congenital dysfibrinogenmia bleeding disorder. These mutations alter the codon coded for the amino acid arginine at either the 35th position of FGA (termed Arg35; see fibrinogen Metz1 and fibrinogen Bicetre in the Table below) and or the 301st position of FGG (termed Arg301; see fibrinogen Baltimore IV in the Table below).[2]