33.1 Hemophilia

Hemophilia is a hereditary recessive X-linked bleeding disorder which mainly affects male individuals since they carry only one X chromosome. Females are carriers of this disease under heterozygous condition and they bear this disease only in recessive homozygous condition. This disorder highly compromises with the blood clotting efficiency of the individual. The individual is unable to clot or coagulate the blood. Clotting of blood is essential to stop bleeding in case of injury.

Three conditions of hemophilia have been defined hemophilia A, hemophilia B and hemophilia C

33.1.1  Hemophilia A is a recessive X-linked genetic disorder, the cause of which is the lack of a functional factor VIII (anti hemophilic factor). Almost 80% of hemophilia cases are of hemophilia A type. This disorder presents itself in 1 out of 10000 male live births. The cause behind hemophilia A is the mutated factor VIII gene.

33.1.2  Hemophilia B is also a recessive X-linked genetic disorder the cause of which is the lack of a functional factor IX (Christmas factor). This disease is also known as Christmas disease. Almost 20% of hemophilia cases. Are of hemophilia B type. This disorder presents itself in 1 out of 34,000 male live births. The cause behind hemophilia B is the mutated factor IX gene.

33.1.3 Hemophilia C unlike the hemophilia A and B is not a recessive X-linked disorder but it is an autosomal genetic disorder the cause of which is the lack of functional factor XI. Haemophilia C is incompletely recessive because even in heterozygous individuals high amount of bleeding has been reported. The cause behind hemophilia C is the mutated factor XI present on chromosome number 4.

The schematic diagrams below (figure 33.1) may be referred to understand the functionalities of the factor VIII, IX and XI. The implications associated with the mutation in these factors and their impact on the clotting mechanism can thus be understood. This disease causes death of individuals who meet with accidents as well as individuals where internal haemorrhage takes place. This disease needs to be seriously addressed.