Hemophilia

Hemophilia is an inherited disorder of blood-clotting system. It was first described by Babylonian Jews more than 1700 years ago. In the 19th century, Queen Victoria passed the disease to her son Leopold and, through several of her daughters, to various royals across the continent, including the royal families of Spain, Germany and Russia (more info). For this reason it was once popularly called "the royal disease". 

Symptoms

The symptoms of hemophilia include:

• Easy bruising.
• Frequent nosebleeds.
• Excessive bleeding after dental work.
• Excessive bleeding after injuries or operations.
• Prolonged bleeding after circumcision

Causes

The major function of blood-clotting system is to stop bleeding. Several proteins, called clotting factors, are involved in the clotting process. Hemophilia is caused by deficiency in one of clotting factors.

• Hemophilia A. This is the most common type of hemophilia, resulting from deficiency in clotting factor VIII.
• Hemophilia B. This type is caused by deficiency in clotting factor IX.
• Hemophilia C. This type results from deficiency in clotting factor XI.

Each protein is produced from a specific gene in DNA. A defective gene will produce non-functional proteins. Hemophilia A or B occurs almost always in males. This is because the gene responsible for the production of clotting factor VIII or IX is located on the X chromosome. A female has two X chromosomes whereas a male has only one X chromosome. For females, if any gene in an X chromosome becomes defective, the same gene in another X chromosome can still produce functional proteins. Therefore, most females who have a defective gene in the X chromosome are simply carriers and exhibit no signs or symptoms of the so-called "X-linked disorders" such as hemophilia A or B.

Hemophilia C can occur in both males and females. The gene for the clotting factor XI is located on chromosome 4.

Treatment

At present, hemophilia is treated with infusion of clotting factor, either from donated human blood or from genetically engineered products. For mild cases, the hormone desmopressin (DDAVP) may be slowly injected into the veins to stimulate release of clotting factor.

In the near future, it is hoped that the disease can be cured by gene therapy. Development along this line has reached the clinical trial stage, and results so far have been encouraging.