Factor 8 and 9 are two of the many proteins in blood, which are important for normal control of bleeding. Therefore, the deficiency of these factors will cause bleeding tendency known as haemophilia A and B respectively.
The underlying pathology is a sex linked disorder ie the abnormal factor 8 or 9 gene carried on the X chromosome will transmit the disease. Since each male has only one copy of X chromosome from his mother, he will be affected if his X chromosome is abnormal. Unlike the male, each female has two copies of X-chromosomes (one from father and the other from mother) and though she will not be affected when one copy is abnormal, she will be a carrier and can pass down the gene to her children. However, there are very rare situations where both her copies are abnormal e.g. when the mother is a carrier and the father is a haemophiliac, or when there is a spontaneous mutation in the genes then a female hemophilia can occur. Thus in practice, almost all the hemophilia patients are male.
Clinically, haemophilia often present with deep bleeding (eg. intramuscular bleeding, joint bleeding) and diagnosis of adult haemophilia can be ascertained by measuring factor 8 or 9 in the blood. Furthermore, genetic study on chorionic villous tissue in early pregnancy can also be performed for intrauterine diagnosis. Similar genetic study can also be used to screen the relatives for a complete family history.
All bleeding episodes have to be treated promptly by increasing the level of factor 8 or 9 as necessary. Increasing blood factors can be achieved by either stimulating release of factor (eg. using DDAVP) or by infusion of cryoprecipitate or external factor concentrates. There are various preparations of factor concentrates eg. pooled donor concentrates (from many blood donors) or recombinant concentrates (from genetic manipulations of animal models to produce human factors). The administration of factors could be done by a medical professional or be taught to the patients/relatives (ie home treatment) in order to decrease their dependency on hospital treatment.
However, there are problems with the administration of foreign factor 8 or 9 eg. developing antibodies against these factors, minimal risk of contracting infections (eg. hepatitis C, hepatitis B, HIV, CJD), and allergic reactions. Intensive study in gene therapy (ie to correct the abnormal gene in haemophilia directly) is currently undertaken in several major centres. There is hope that this would provide a cure in future.
The National Haemophilia Registry was set up at SGH in August 1995 to collect all data on Hemophilia and to assist treatment of all hemophilia patients and affected family members.