Hemophilia is a term for whole group of genetic-related diseases that manifest by blood coagulation disorders (increased bleeding).
Hemophilia is a genetically determined disorder of some proteins of the coagulation cascade. The coagulation (clotting) cascade is described in text about the Factor V Leiden (Leiden mutation). It is a very complex system consisting of many proteins that are traditionally labeled with Roman numerals. The clotting system should be activated by an injury of blood vessels and its final reaction is the transformation of fibrinogen to fibrin. The fibrin forms net-like fibers. These fibers are essential for local stabilization of platelets and formation of a blood clot.
In hemophilia, there is a genetic disorder of the X chromosome and this causes lack of a specific coagulation factor. In severe cases, the clotting factor is completely absent. The most common type is hemophilia A with disorder of factor VIII and less frequent is hemophilia B with defective factor IX. The deficiency of any of these factors disrupts the coagulation cascade and decreases the coagulation process.
As stated above, the disease is linked to a genetic defect of chromosome X resulting in disorder of coagulation factor production. This is a very disadvantageous situation for males as they have only one X chromosome. If a male has the defective form of X chromosome from his mother, he will inevitably suffer from symptoms of the disease. Women, on the other hand, have two X chromosomes - one from mother and one from father. Even with one defective X chromosome, the other healthy chromosome is sufficient for proper formation of the clotting factors. Such woman does not have symptoms of hemophilia but she is a carrier as she can pass copy of her defective X chromosome to her children. And yes, there is a very little chance that a woman gets two defective chromosomes (when a hemophilic man has a child with a carrier mother) but such condition is incompatible with life and the female fetus dies in mother’s womb. Therefore, hemophilia occurs only in men.
A typical example - healthy man with chromosomes X and Y has children with seemingly healthy woman which is transmitter having a healthy X chromosome and chromosome sick "red X". They may have in terms of hemophilia four types of children depending on which chromosome is transmited to his offspring. The baby no. 1 is healthy woman, child no. 2 is a transmitter woman (as a mother), baby no. 3 is healthy man and child no. 4 is a man with hemophilia.
Note: Although hemophilia is probably the most known bleeding disorder, it is much rarer than the practically unknown Von Willebrand disease.
Hemophilia is characterized by excessive bleeding of a various severity ranging from mere bruising to fatal internal hemorrhage. The patient usually suffers from long and heavy bleeding following even little injuries, frequent bruising, nosebleeds, blood in stool and blood in urine occurrence. Quite serious complication is an intracerebral hemorrhage (hemorrhagic stroke).
Information of positive family history is crucial in a man with the above-mentioned symptoms. In blood test we find prolonged blood clotting time (APTT test) and the diagnosis can be confirmed by special examination of activity of clotting factors VIII and IX.
As hemophilia is a congenital disease, it can not be prevented. However, when there is hemophilia present in a family, it is possible to perform genetic testing to evaluate risk of disease for children even before they are born.
Patients with hemophilia should avoid situations that increase risk of injuries. In addition, modern medicine provides us with an elegant therapy. Does the patient miss a clotting factor? We can produce it artificially and administer it to the patient by injections. The treatment is life-long. When there is a serious bleeding, blood transfusions may be needed.
A person with a confirmed diagnosis of hemophilia should inform any doctor with whom he comes in contact. Prescription of any drug decreasing blood clotting can be fatal.