A primer on hemophilia.
A: Hemophilia is a bleeding disorder in which blood has insufficient amount of certain proteins called blood clotting factors that are needed for blood clotting or coagulation, i.e., the formation of a blood clot or coagulate.
Blood clotting, which involves the interplay of cellular elements called platelets and a number of clotting factors that bear common and Roman numeral names, plays an important role in maintaining the integrity of blood vessels. When a blood vessel is injured, which is a frequent occurrence, the damaged area must be clogged with a blood clot to stop blood from leaking out of the vessel. In normal people, this occurs immediately resulting in minimal loss of blood. But in people with hemophilia, formation of a blood clot is delayed resulting in prolonged bleeding.
There are several types of hemophilia. They are classified according to which clotting factor is deficient. In hemophilia A (classic hemophilia), the most common type, which accounts for 90 percent of all hemophilia cases, factor VIII (antihemophilic factor) is deficient. In hemophilia B (Christmas disease), the second most common type, factor IX (plasma thromboplastin component) is lacking. While in hemophilia C, a mild and rare form of the disease, factor XI (plasma thromboplastin antecedent) is deficient.
The lack of a clotting factor in hemophilia is caused by a defect in the gene that carries the instruction on how the clotting factor should be made. The genes related to clotting factor are located in the X chromosome, a sex chromosome--that is why hemophilia is referred to as a sex-linked disorder.
Everyone has a pair of sex chromosomes. In females, both are X chromosomes--one inherited from their mother and the other from their father. In males, one sex chromosome is an X chromosome, which they inherited from their mother while the other is a Y chromosome that came from their father.
A male who has a faulty hemophilia gene on his X chromosome will have hemophilia. In contrast, a female with a defective hemophilia gene on one of her X chromosomes does not become sick because the hemophilia gene is a recessive one--it does not manifest in the presence of another X chromosome. A female must have the faulty gene on both of her X chromosomes to have hemophilia, which rarely occurs.
The female with a defective hemophilia gene serves as a "carrier" that passes on the faulty gene to some of her sons and daughters. Her sons who inherit the defective gene will have hemophilia while her daughters who inherit the defective gene will serve as carriers. In contrast, a male who carries the defective gene transmits the gene to all his daughters who then act as carriers, but not to his sons because the sex chromosome his son inherits from him is the Y chromosome. Hence, the son of a male hemophiliac will be free of the disease.
The inheritance pattern of hemophilia is the reason why the disease affects mainly males who invariably inherited the disease from their mother. About one in 5,000 males are born with hemophilia. In the Philippines, experts estimate that 6,000 to 8,000 Filipinos suffer from hemophilia, but only about a thousand have been diagnosed.
Although hemophilia is generally inherited, sometimes, it can be acquired. This happens when the body forms antibodies that attack the clotting factors or when the involved gene spontaneously mutates or becomes defective.
People with hemophilia bleed easily and their bleeding takes a longer time to stop. They are susceptible to prolonged bleeding from small cuts; bruises and hematomas; and, frequent and hard to stop nose and gum bleeds. But, of more serious concern in these people is internal bleeding. Bleeding into the joints, usually of the knees, elbows, and ankles, causes swelling and pain and can lead to chronic arthritis while bleeding in the digestive and urinary tracts gives rise to bloody stools and urine. Bleeding into the different organs can be life threatening--as when it is profuse or when it occurs in a vital organ such as the brain--or can cause permanent damage in these organs.
Hemophilia can easily be diagnosed with the aid of blood tests. People who experience frequent spontaneous and/or prolonged bleeding should undergo these tests to rule out or rule in the disease.
Hemophilia cannot be cured yet. Current treatment is replacement of the missing blood clotting factor by transfusing commercially prepared factor concentrates. With proper treatment and self-care, most people with hemophilia can maintain an active, productive lifestyle.