The clotting cascade, as it is usually called, is the series of events required to form the final clot. The cascade uses a technique called amplification to rapidly produce the proper sized fibrin clot from the small number of molecules initially activated by the injury.
In Hemophilia, certain clotting factors are either decreased in quantity, absent, or improperly formed. Because the clotting cascade uses amplification to rapidly plug up a bleeding area, absence or inactivity of just one clotting factor can greatly increase bleeding time.
Hemophilia A is the most common type of bleeding disorder and involves decreased activity in factor Vlll. There are three levels of factor Vlll deficiency: severe, moderate, and mild. This classification is based on the percentage of normal factor Vlll activity present:
- Individuals with less than 1% of normal factor Vlll activity level have severe hemophilia. Half of all people with hemophilia A fall into this category. Such individuals frequently experience spontaneous bleeding, most frequently into their joints, skin, and muscles. Surgery and trauma can result in life-threatening hemorrhage, and must be carefully managed.
- Individuals with 1-5% of normal factor Vlll activity level have moderate hemophilia, and are at risk for heavy bleeding after seemingly minor traumatic injury.
- Individuals with 5-40% of normal factor Vlll activity level have mild hemophilia, and must prepare carefully for any surgery or dental procedures.
Individuals with hemophilia B have symptoms very similar to those of hemophilia A, but but the deficient factor is factor IX. This type of hemophilia is also known as Christmas disease.
Hemophilia C is very rare, and much more mild than hemophilia A or B; it involves factor XI.
Hemophilia Affects between one in 5,000 to one in 10,000 males in most populations.
- One recent study estimated the prevalence of hemophilia was 13.4 cases per 100,000 U.S. males (10.5 hemophilia A and 2.9 hemophilia B). By race/ethnicity, the prevalence was 13.2 cases/100,000 among white, 11.0 among African-American, and 11.5 among Hispanic males.
Complication/ Life outlook
- Hemophilia is an X-linked genetic disorder, which means that it's passed from mother to son on the X chromosome. If the mother carries the gene for hemophilia on one of her X-chromosomes, each of her sons will have a 50% chance of having hemophilia.
- Because it is an inherited genetic disease, hemophilia cannot be prevented. If you or any of your immediate family members (parents or siblings) have hemophilia.
- Carrier testing procedure
- Direct mutation testing
- Linkage (indirect) testing
- Need for carrier testing for hemophilia
- Prenatal testing