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Haemophilia A (also spelled Hemophilia A or Hæmophilia A) is a blood clotting disorder caused by a mutation of the factor VIII gene, leading to a deficiency in Factor VIII. It is the most common hemophilia. Inheritance is X-linked recessive; hence, males are affected while females are carriers or very rarely display a mild phenotype. 1 in 5,000 males are affected.
Additional recommended knowledge
Signs and symptoms
Hemophilia leads to a severely increased risk of bleeding from common injuries. The sites of bleeding are:
The muscle and joint hemorrhages are quite typical of hemophilia, while digestive tract and cerebral hemorrhages are also germane to other coagulation disorders.
The diagnosis may be suspected as coagulation testing reveals an increased PTT in the context of a normal PT and bleeding time. The diagnosis is made in the presence of very low (<10 IU) levels of factor VIII. A family history is frequently present, although not essential. Recently, genetic testing has been made available to determine an individual's risk of attaining or passing on Haemophilia.
The most important differential diagnosis is that of hemophilia B (also known as Christmas disease) or von Willebrand disease. The former is usually considered if factor VIII levels are normal in a person with a haemophilia phenotype. The latter is excluded on routine testing for that condition.
A very small minority of patients have antibodies against factor VIII that impair its functioning. Management of these patients is more complicated (see below).
Most haemophilia patients require regular supplementation with intravenous recombinant factor VIII. This is highly individually determined. Apart from "routine" supplementation, extra factor concentrate is given around surgical procedures and after trauma. In children, an easily accessible intravenous port (e.g. Port-a-Cath) may have to be inserted to minimise frequent traumatic intravenous cannulation. These devices have made prophylaxis in hemophilia much easier for families because the problems of "finding a vein" for infusion two to three times a week are eliminated. However, there are risks involved with their use, the most worrisome being that of infection. Studies differ but some show an infection rate as high as 50 percent. These infections can usually be treated with intravenous antibiotics but sometimes the device must be removed. Also, there are other studies that show a risk of clots forming at the tip of the catheter. Still, many families have chosen to use the device in spite of the risk because of the benefits. Like any other procedure, one must weigh the risks and benefits.
Some may manage on desmopressin, if the clotting factor is still partially active.
A particular therapeutic conundrum is the development of "inhibitor" antibodies against factor VIII due to frequent infusions. These probably develop as the body recognises the factor VIII as foreign, as the body does not have its own "copy". The problem is that in these patients, factor VIII infusions are ineffective. Recently activated factor VII (NovoSeven®) has become available as a treatment for haemorrhage in patients with haemophilia and factor inhibitors.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Haemophilia_A". A list of authors is available in Wikipedia.|