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Hemophilia is a hereditary genetic disease that prevents correct blood clotting.
Hemophilia is a hereditary genetic disease that prevents correct blood clotting due to a deficiency of some coagulating factor, which is a kind of protein that form blood clots, helping to stop bleeding.
Due to the deficiency of any of these coagulation factors, wounds take longer to heal, and bleeding goes on for longer. One of the risks that this disease poses is uncontrolled internal bleeding, which can be due to an injury or even occur spontaneously.
There are two main types of hemophilia: hemophilia A, or classic hemophilia, in which coagulation factor VIII is affected, and hemophilia B, also known as Christmas disease, in which the function of coagulation factor IX is altered. Both types are characterized by spontaneous bleeding or bleeding caused by trauma. Hemorrhage can occur in joints and muscles, usually in the knees, elbows, and ankles, leading to rigidity, pain, major joint damage, disability, and even death in severe cases. Other symptoms are extensive bruising and long-lasting bleeding after sustaining a wound or trauma.
The severity of hemophilia depends on the extent to which coagulation factor is lacking. Patients with mild hemophilia show between 5% and 30% of normal coagulation factor activity. Patients with moderate hemophilia show between 1% and 5% of normal coagulation factor activity. Patients with severe hemophilia show less than 1% of normal coagulation factor activity. In the latter case, patients may often bleed without apparent cause; however, mild and moderate patients rarely bleed without a cause.
There is an uncommon type of hemophilia B, known as hemophilia B Leyden, in which patients have bleeding episodes during childhood, but this symptom virtually stops after puberty.
Although there is no current cure for hemophilia, treatment is highly effective. It consists of intravenous injections of the appropriate coagulation factor to stop bleeding. Early treatment of these hemorrhage episodes is essential to prevent pain and damage to joints, muscles, and organs. Nowadays, with appropriate treatment, people suffering from this disorder can lead normal, healthy lives.
Hemophilia A is caused by mutations in the F8 gene, which encodes a protein known as coagulation factor VIII, while hemophilia B is caused by mutations in the F9 gene, which generates coagulation factor IX. Coagulation factors are proteins involved in the blood clotting process. Mutations in the F8 and F9 genes lead to the generation of abnormal coagulation factors, or to a decrease in their levels, and result in altered blood clot formation. Mutations causing severe hemophilia may cause that coagulation factors VIII or IX are almost completely absent.
Hemophilia is considered a rare disease due to its low prevalence in the population. Both types of hemophilia are much more common in men than in women due to its inheritance pattern. Hemophilia A affects approximately 1 in 5,000 male newborns, while hemophilia B affects 1 in 20,000.
Hemophilia is a hereditary X-linked recessive disease, i.e. the genes associated with this disorder are located on the X chromosome. In the case of men, who only have one X chromosome, one altered copy of the gene in each cell is sufficient for the disease to develop. In women, who have two X chromosomes, the mutation must be present in both chromosomes for the disease to develop; this is much more unlikely and, therefore, this disease is almost exclusively seen in men.
In the case that the mother is a carrier and the father is healthy, each one of their male offspring will have a 50% probability of developing hemophilia, while female offspring will have a 50% probability of being carriers. If the father has hemophilia and the mother does not, none of the children will suffer from the disease, but all the daughters will be carriers of the faulty gene.
Approximately one in three new cases is due to a new mutation; therefore, no family history of hemophilia exists in these cases.
A genetic counseling consultation s recommended to future parents who suffer from the disease or are aware of cases in the family; in this way, they can know the risk of transmitting the disease to their offspring, perform the genetic tests that are deemed necessary, and take the appropriate prevention measures.