Hemophilia a

This disease is the most common disorder of blood clotting, resulting from a deficiency of factor VIII coagulation. In total there are XV factors of blood coagulation. All of them are located in the blood plasma. Hemophilia A is the only one among all diseases of blood clotting disorder with a recessive, X-linked inheritance inheritance.

Located in the X chromosome, the hemophilia gene is transmitted from a man with hemophilia to all his daughters, and therefore they inevitably become transmitters of the disease. Simultaneously, all sons of a sick man remain healthy, as they receive their only X-chromosome from a healthy mother. In women who are carriers of one X chromosome with a mutant hemophilia gene, half of the sons have chances to be born sick( as there is an equal chance of getting a mutated or normal X chromosome from the mother), and half of the daughters have chances to become transmitters of the disease. This rule is invariably confirmed only in a large population, but not in individual families, where sometimes all sons can suffer from hemophilia or, conversely, only healthy boys are born.

Women who carry the same mutant gene, bleeding, usually do not suffer, since the second normal X chromosome provides the formation of 1/4-1 / 2 of the fraction of factor VIII required for normal blood clotting, which in most cases is sufficient. However, the factor VIII content can vary widely( from 60 to 250%).In this regard, in some transmitters, the level of factor VIII in plasma can be only 11-20%, which creates a threat of bleeding in injuries, operations and childbirth.

The severity of hemorrhagic phenomena( bleeding syndrome) in hemophilia is strictly interrelated with the degree of deficiency of factor VIII in plasma, the level of which in some families with hemophilia is genetically strictly programmed. A clear dependence of the frequency and severity of bleeding on the level of deficiency of the factor in the blood plasma is disturbed in case of heavy blood loss as a result of injuries and surgeries.