Haemophilia A
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Haemophilia A (also spelt 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; hence, males are affected while female are carriers or very rarely display a mild phenotype. 1 in 10,000 males are affected.
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Signs and symptoms
Hemophilia leads to a severely increased risk of bleeding from common injuries. The sites of bleeding are:
The muscle and joint haemorrhages are quite typical of haemophilia, while digestive tract and cerebral haemorrhages are also germane to other coagulation disorders.
Diagnosis
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. Nowadays, genetic testing may also be performed.
The most important differential diagnosis is that of hemophilia B 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 has antibodies against factor VIII that impair its functioning. Management of these patients is more complicated (see below).
Therapy
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.
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.
External links
- Template:OMIM
- Your genes your health (http://www.yourgenesyourhealth.org/ygyh/mason/ygyh.html?syndrome=hemo§ion=whatisit&video=0)