What is Hemophilia? For the Non-Scientist: Genetic Disorders

Hemophilia is a hereditary genetic disease in which the body of an individual is unable to produce the factors needed to successfully create and maintain a blood clot to stem blood loss from injury.

To understand hemophilia, you must first understand how the body protects itself from excessive blood loss as a result of bruises to the blood vessels through a process called coagulation.

When a blood vessel sustains a bruise, its surface covering called the endothelium, is breached leaving a underlying collagen matrix and blood begins to leak from the point of damage. Substances in the blood called platelets attach themselves to the collagen creating a temporary clot. These platelets send out signals to other platelets to join them, at the same time the platelets send out different signals to initiate what is called a thrombin burst.

The protein thrombin is what allows other clotting agents to switch to there active form which can only occur after the primary clot is established. These two newly activated agents work together to create a net like network called fibrin, which holds and maintains the clot until the damage site is repaired, then the entire clot is disposed of by anticoagulant agents. It is one out of the two fibrin creating clotting factors called FVIII and FIX that a hemophiliac lacks.

Depending on the type of hemophilia, a person can either have a deficient of FIII resulting in hemophilia A, the most common, or a deficient of FIX will lead to hemophilia B. Without these factors a clot can not be maintained and excessive bleeding ensues from the smallest of injuries. The concentration of the deficient clotting factors determines how severe the case is; from very mild to severe.

Hemophilia is a hereditary genetic disease, meaning it is cause by an abnormality in the genes. Hemophiliacs are almost exclusively males who have inherit it from their mothers.

When a woman with her two X chromosomes has the hemophilia trait, she does not have to be a victim of the disease, but she does have the potential to give the trait to her daughters and a 50% chance of giving the disease itself to her sons. This is because the hemophilia gene is X linked, meaning it is carried by the X chromosome.

Since the gene for hemophilia is recessive, it is shadowed by the dominant normal gene on the other X chromosome. Therefore a woman with the trait or the disease can pass the recessive gene on to her daughter, but the other X chromosome that she get from her father, if he is unaffected by the disease, will shadow the recessive gene ensuring that she only has the trait. Only if her father had the disease as well will she have.

However, because males have only one X chromosome, which the son inherit from his mother, if the X chromosome he inherits is the one with the recessive gene, then the Y chromosome which is the recessive chromosome will have no power to shadow the recessive hemophilia gene, therefore it will express itself in the manifestation of the disease.

Treatment includes regular transfusions of the missing clotting factor. These can be obtained through the purification of donated blood or artificial clotting agent known as highly purified recombinant factor concentrates.

If the case is discovered and controlled early on and the hemophiliac is responsible with their condition and receives the right treatment, he can live a long and productive life, not so unlike a normal person's.