C, T, A, G) at these sites before>after the mutation; c) the name of the altered fibrinogen peptide (Aα, Bβ, or λ) and the amino acids (using standard abbreviations) occurring before-after the mutation at the numbered amino acid(s) sites in the circulating mutated fibrinogen; d) the pathophysiology for the mutated fibrinogens misfunction(s); and e) the clinical consequence(s) of the mutation. Unless noted as a deletion (del) or frame shift (fs), all mutations are missense or nonsense mutations. A nonsense mutation causing a premature stop codon and thereby a shorten polypeptide chain is notated by an X (PSC) after the altered amino acid codon. Diagnosis
Hypodysfibrinogenemia is usually diagnosed in individuals who: have a history of abnormal bleeding or thrombosis or are a close blood relative of such an individual. Initial laboratory findings include a decrease in serum fibrinogen mass levels as measured by immunoassay plus a reduction in inducible blood clot formation so that the ratio of functionally-detected fibrinogen mass (i.e. detected in induced clots) to immunoassay-detected fibrinogen mass is abnormally low, i.e. <0.7. This contrast with individuals with congenital dysfibrinogenemia who exhibit normal levels of fibrinogen as measured by immunoassay but low functionally-detected to immunoassay-detected fibrinogen mass ratios, i.e. <0.7. Where available, specialized laboratories can conduct studies to define the exact gene mutation(s) and fibrinogen abnormalities underlying the disorder. Treatment
Blood relatives of the proband case should be evaluated for the presence of hypodysfibrinogenemia.
Bleeding is more frequent and severe in women of child-bearing age; these women may suffer miscarriages, menometrorrhagia, and excessive bleeding during child birth and/or the postpartum period. Excessive bleeding following major or minor surgery, including dental extractions, occurs in both females and males with the disorder. Thrombotic complications of the disorder are often (~50%) recurrent and can involve central and peripheral arteries, deep and superficial veins. Thrombotic events may be serious and involve occlusion of a cerebral artery leading to stroke, splanchnic venous thrombosis, and pulmonary thrombosis presumptively secondary to deep vein thrombosis. Fibrinogen
Circulating fibrinogen is a glycoprotein made of two trimers each of which is composed of three polypeptide chains, Aα (also termed α) encoded by the FGA gene, Bβ (also termed β) encoded by the FGB gene, and γ encoded by the FGG gene. All three genes are located on the long or "q" arm of human chromosome 4 (at positions 4q31.3, 4q31.3, and 4q32.1, respectively) and are the sites where mutations occur that code for a dysfunctional fibrinogen and/or reduced fibrinogen levels which are the cause of congenital hypodysfibrinogenemia. Pathophysiology
Congenital hypodysfibrinogenemia is inherited as an autosomal dominant disorder caused by at least 32 different types of single mutations. Ten of these mutations are in the fibrinogen alpha chain gene (also termed the FGA gene), 5 in the fibrinogen beta chain gene (also termed the FGB gene), and 17 in the fibrinogen gamma chain gene (also termed the FGG gen).