Congenital Afibrinogenemia is a rare disorder characterized by absence of a certain substance (protein) in the blood that is essential in the blood clotting (coagulation) process. This protein is known as fibrinogen or coagulation factor I. Affected individuals may be susceptible to severe bleeding (hemorrhaging) episodes, particularly during infancy and childhood. Congenital Afibrinogenemia is thought to be transmitted as an autosomal recessive trait.
Congenital Afibrinogenemia is a very rare blood disorder in which the patient is born with little or no fibrinogen in the circulating blood. Fibrinogen is a protein that is needed to form blood clots. When this protein is absent, the blood does not coagulate which can cause the patient to hemorrhage.
Two thirds of the patients with Congenital Afibrinogenemia have bleeding problems from infancy on. The severity and frequency of bleeding from surgery or trauma can vary from mild to severe.
Infants may have severe hemorrhaging during the first few days of life. Typically the hemorrhaging can be noticed from the umbilical cord, in the stools, when vomiting, after circumcision, from the use of forceps during delivery and/or in collections of blood that become trapped in the skin tissue (hematomas).
Other symptoms of Congenital Afibrinogenemia may be severe bleeding after minor trauma, the loss of baby teeth, or during the extraction of teeth. Patients may also bruise easily and hemorrhage from the gums.
Some patients with Congenital Afibrinogenemia also experience hemorrhaging into a joint (hemarthrosis), nosebleeds, gastrointestinal bleeding, heavy bleeding during menstruation; bleeding in the chest cavity and/or a ruptured spleen.
Congenital Afibrinogenemia is thought to be transmitted as an autosomal recessive trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
Absence or deficiency of fibrinogen is thought to result from abnormal changes (mutations) of one of three genes, known as the fibrinogen alpha-chain (FGA), beta-chain (FGB), or gamma-chain (FGG) genes. These genes have been mapped to the long arm (q) of chromosome 4 (4q28). Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q”. Chromosomes are further subdivided into bands that are numbered.
According to one team of researchers, genetic analysis of individuals with congenital afibrinogenemia within one extended family (i.e., including two siblings and two first cousins) revealed deletion of genetic material from the fibrinogen alpha-chain gene (FGA) on both chromosomes (homozygous deletion). Because previous studies have not detected this homozygous deletion, the study’s researchers indicate that other genetic abnormalities (mutations) may play some role in causing the disorder in some affected individuals.
Congenital Afibrinogenemia is a rare disorder that affects males and females in equal numbers. Approximately one hundred and thirty cases have been recorded in the medical literature.
Patients with Congenital Afibrinogenemia may be treated with infusions of cryoprecipitate concentrates. This is prescribed to raise the fibrogen level in the blood permitting clots to form.
Fibrogen concentrates may be given but there is a risk of contracting an infectious disorder. Cryoprecipitate is the preferred treatment.
Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.
Research on birth defects and their causes is ongoing. The National Institutes of Health (NIH) is sponsoring the Human Genome Project which is aimed at mapping every gene in the human body and learning why they sometimes malfunction. It is hoped that this new knowledge will lead to prevention and treatment of genetic disorders in the future.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
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Cecil Textbook of Medicine, 19th Ed.: James B. Wyngaarden, and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1990. P. 1073.
Hematology, 4TH Ed,: William J. Williams, et al., Editors; McGraw-Hill, Inc. Pp. 1474-75.
Birth Defects Encyclopedia, Mary Louise Buyse, M.D., Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 62-63.
Deletion of the Fibrinogen Alpha-Chain Gene (FGA) Causes Congenital Afibrogenemia. M. Neerman-Arbez et al.; J Clin Invest (Jan 1999; 103(2)). Pp. 215-18. Published erratum in J Clin Invest (Mar 1999; 103(5)). P. 759.
Prophylactic Cryoprecipitate in Congenital Afibrinogenemia: R.C. Rodriguez et al.; Clin Pediatr (November 1988; 27(11)). Pp. 543-45.
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Online Mendelian Inheritance in Man (OMIM). Victor A. McKusick, Editor; Johns Hopkins University, Last Edit Date 3/16/99, Entry Number 202400; Last Edit Date 3/16/99, Entry Number 134820; Last Edit Date 6/30/98, Entry Number 134830; Last Edit Date12/2/98, Entry Number 134850.
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