Hemophilia pathophysiology: Difference between revisions
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*Changes in the ''F8'' [[gene]] are responsible for hemophilia A, while mutations in the ''F9'' gene cause hemophilia B. The ''F8'' gene provides instructions for making a protein called coagulation [[factor VIII]]. A related protein, coagulation [[factor IX]], is produced from the ''F9'' gene. Coagulation factors are proteins that work together in the blood clotting process. After an injury, blood clots protect the body by sealing off damaged blood vessels and preventing excessive blood loss. | *Changes in the ''F8'' [[gene]] are responsible for hemophilia A, while mutations in the ''F9'' gene cause hemophilia B. The ''F8'' gene provides instructions for making a protein called coagulation [[factor VIII]]. A related protein, coagulation [[factor IX]], is produced from the ''F9'' gene. Coagulation factors are proteins that work together in the blood clotting process. After an injury, blood clots protect the body by sealing off damaged blood vessels and preventing excessive blood loss. | ||
*Mutations in the ''F8'' or ''F9'' gene lead to the production of an abnormal version of coagulation | *Mutations in the ''F8'' or ''F9'' gene lead to the production of an abnormal version of coagulation factor VIII or coagulation factor IX, or reduce the amount of one of these proteins. The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury. These problems with blood clotting lead to continuous bleeding that can be difficult to control. The mutations that cause severe hemophilia almost completely eliminate the activity of coagulation factor VIII or coagulation factor IX. The mutations responsible for mild and moderate hemophilia reduce but do not eliminate the activity of one of these proteins. | ||
*Another form of the disorder, known as [[acquired]] hemophilia, is not caused by inherited gene mutation. This rare condition is characterized by abnormal bleeding into the skin, muscles, or other soft tissues, usually beginning in adulthood. Acquired hemophilia results when the body makes specialized proteins called auto antibodies that attack and disable coagulation | *Another form of the disorder, known as [[acquired]] hemophilia, is not caused by inherited gene mutation. This rare condition is characterized by abnormal bleeding into the skin, muscles, or other soft tissues, usually beginning in adulthood. Acquired hemophilia results when the body makes specialized proteins called auto antibodies that attack and disable coagulation factor VIII. The production of auto antibodies is sometimes associated with pregnancy, immune system disorders, cancer, or allergic reactions to certain drugs. In about half of cases, the cause of acquired hemophilia is unknown.<ref>{{Cite web | title = NIH Hemophilia Pathophysiology| url =http://ghr.nlm.nih.gov/condition/hemophilia }}</ref> | ||
[[Image:Images_266_(1).gif |200px|thumb|center|The image shows one example of how the hemophilia gene is inherited. In this example, the father doesn't have hemophilia (that is, he has two normal chromosomes—X and Y). The mother is a carrier of hemophilia (that is, she has one hemophilia gene on one X chromosome and one normal X chromosome)]] | [[Image:Images_266_(1).gif |200px|thumb|center|The image shows one example of how the hemophilia gene is inherited. In this example, the father doesn't have hemophilia (that is, he has two normal chromosomes—X and Y). The mother is a carrier of hemophilia (that is, she has one hemophilia gene on one X chromosome and one normal X chromosome)]] | ||
[[Image:Images_267.gif |200px|thumb|center|The image shows one example of how the hemophilia gene is inherited. In this example, the father has hemophilia (that is, he has the hemophilia gene on the X chromosome). The mother isn't a hemophilia carrier (that is, she has two normal X chromosomes)]] | [[Image:Images_267.gif |200px|thumb|center|The image shows one example of how the hemophilia gene is inherited. In this example, the father has hemophilia (that is, he has the hemophilia gene on the X chromosome). The mother isn't a hemophilia carrier (that is, she has two normal X chromosomes)]] | ||
Revision as of 18:24, 1 September 2015
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Hemophilia Microchapters |
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Hemophilia pathophysiology On the Web |
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Risk calculators and risk factors for Hemophilia pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Development of hemophilia is the result of multiple genetic mutations. The genes involved in the pathogenesis of hemophilia include the F8 gene in hemophilia A and F9 gene in hemophilia B.
Pathophysiology
- Hemophilia is caused by a mutation or change, in one of the genes, that provides instructions for making the clotting factor proteins needed to form a blood clot. This change or mutation can prevent the clotting protein from working properly or to be missing altogether. These genes are located on the X chromosome. Males have one X and one Y chromosome (XY) and females have two X chromosomes (XX). Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.
- The X chromosome contains many genes that are not present on the Y chromosome. This means that males only have one copy of most of the genes on the X chromosome, whereas females have 2 copies. Thus, males can have a disease like hemophilia if they inherit an affected X chromosome that has a mutation in either the factor VIII or factor IX gene. Females can also have hemophilia, but this is much rarer. In such cases both X chromosomes are affected or one is affected and the other is missing or inactive. In these females, bleeding symptoms may be similar to males with hemophilia.
- A female with one affected X chromosome is a "carrier" of hemophilia. Sometimes a female who is a carrier can have symptoms of hemophilia. In addition, she can pass the affected X chromosome with the clotting factor gene mutation on to her children.
- Even though hemophilia runs in families, some families have no prior history of family members with hemophilia. Sometimes, there are carrier females in the family, but no affected boys, just by chance. However, about one-third of the time, the baby with hemophilia is the first one in the family to be affected with a mutation in the gene for the clotting factor.[1]
Genes affected in Hemophilia
- Changes in the F8 gene are responsible for hemophilia A, while mutations in the F9 gene cause hemophilia B. The F8 gene provides instructions for making a protein called coagulation factor VIII. A related protein, coagulation factor IX, is produced from the F9 gene. Coagulation factors are proteins that work together in the blood clotting process. After an injury, blood clots protect the body by sealing off damaged blood vessels and preventing excessive blood loss.
- Mutations in the F8 or F9 gene lead to the production of an abnormal version of coagulation factor VIII or coagulation factor IX, or reduce the amount of one of these proteins. The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury. These problems with blood clotting lead to continuous bleeding that can be difficult to control. The mutations that cause severe hemophilia almost completely eliminate the activity of coagulation factor VIII or coagulation factor IX. The mutations responsible for mild and moderate hemophilia reduce but do not eliminate the activity of one of these proteins.
- Another form of the disorder, known as acquired hemophilia, is not caused by inherited gene mutation. This rare condition is characterized by abnormal bleeding into the skin, muscles, or other soft tissues, usually beginning in adulthood. Acquired hemophilia results when the body makes specialized proteins called auto antibodies that attack and disable coagulation factor VIII. The production of auto antibodies is sometimes associated with pregnancy, immune system disorders, cancer, or allergic reactions to certain drugs. In about half of cases, the cause of acquired hemophilia is unknown.[2]
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