severe liver disease or because of excessive fibrinogen consumption resulting from, e.g. disseminated intravascular coagulation.Certain gene mutations causing congenital hypfibrinogenemia disrupt the ability of liver cells to secrete fibrinogen. In these instances, the un-mutated gene maintains blood fibrinogen at reduce levels but the mutated gene produces a fibrinogen that accumulates in liver cells sometimes to such extents that it becomes toxic. In the latter cases, liver disease may ensue in a syndrome termed fibrinogen storage disease. Signs and symptoms
Individuals with congenital hypfibringenemia often lack any symptoms are detected by routine lab testing of fibrinogen or when tested for it because close relatives have symptomatic hypofibrinogenemia. Indeed, studies indicate that, among family members with the identical congenital hypofibrinogenemia mutation, some never exhibit symptoms and those that are symptomatic develop symptoms only as adults. No liver disease
Individuals with this disorder are usually less symptomatic than patients with other fibrinogen disorders because their fibrinogen levels are generally sufficient to prevent spontaneous bleeding. Those with particularly low blood fibrinogen levels (<0.5 gram/liter) may develop serious bleeding spontaneously and many with the disorder do so following trauma or surgery. Depending on their fibrinogen levels, women with the disorder may also bleed excessively during delivery and the postpartum period; in rare cases, they may have an increased risk of suffering miscarriages. Individuals with the disorder also experience thrombotic events which may include blockage of large arteries in relatively young patients who have high levels of cardiovascular risk factors.
The assembled protein is passes to the Golgi apparatus where it is glycosylated, hydroxylated, sulfated, and phosphorylated to form the mature fibrinogen glycoprotein that is secreted into the blood. Congenital hypfibrinogenemia results from inherited mutations in one of the three fibrinogen chains that results in the disruption of fibrinogen synthesis, assembly, stability, processing through the endoplasmic reticulum-Golgi apparatus pathway, and/or secretion into the blood.There are >25 fibrinogen mutations that have been associated with hypofibrinogenemia. The following Table lists examples of those mutations which cause hypofibrinogenemia that is not associated with liver injury. The Table gives: a) each mutated proteins trivial name; b) the gene mutated (i.e. FGA, FGB, or FGG), its mutation site (i.e. numbered nucleotide in the gene beginning with the initial nucleotide base at the (start codon) of genomic DNA (as indicated by the "g." notation), and name of the nucleotides (i.e. C, T, A, G) at these sites before>after the mutation; and c) the name of the altered fibrinogen peptide (Aα, Bβ, or λ), the numbered position(s) of the amino acid changed by the mutation in the circulating peptide of the mutated fibrinogen, and the identity of the amino acids before-after the mutation using standard three letter abbreviations. In the Table, fs indicates a mutation that causes a Translational frameshift and consequently a premature stop codon (designated by "X") mutation and translation of a shortened fibrinogen chain, del is a deletion, and ins is an insertion.