Causes

Causes of Hemophilia A

Hemophilia A affects approximately one in ten thousand people (these statistics are often conflicting). Hemophilia is received during birth due to its genetic defects. However, only 70% of hemophiliacs inherit the genetic defect from their parents, while the other 30% receive their disorder through a spontaneous genetic mutation.

 

Sex-Linked Disorders

A few concepts need to be mentioned in order to understand how Hemophilia A is inherited. First of all, every human has a set of chromosomes that determines their gender. Women have a pair of X chromosomes, while men have a set of XY chromosomes. The defect for hemophilia is always carried on the X chromosome, making this disease a sex-linked disorder. Hemophilia primarily affects males, because males only have one X chromosome. When women have a hemophilia-infected X chromosome, her second X chromosome can fulfill the duties of the mutated X chromosome. Women who have only one mutated X chromosome are called carriers. The “carrier” characteristic defines Hemophilia A as a sex-linked recessive disease. Being an x-linked recessive disease makes hemophilia more common in males, creates carrier daughters when there is a hemophiliac father, and is never transmitted from father to son.

 

These two diagrams show how hemophilia is carried on the X chromosome and is passed down to the offspring. The pictures reveal the difference between carriers and those infected. The difference is also validated between the transfer of hemophilia between carrier mothers and infected fathers.

Females rarely inherit Hemophilia A. However the chance is possible. When a hemophiliac father and carrier mother both pass on their flawed X chromosomes, the female offspring will have this blood disorder. It is also possible for a hemophiliac mother and hemophiliac father to pass on the disorder to their daughter.

 

A Spontaneous Mutation

The other 30% of hemophiliacs receive the disease through a spontaneous mutation. This means that some time during gestation, the X chromosome was accidentally defected. Patients who receive Hemophilia A through a spontaneous mutation are often the first in their family to ever have the disease. Once someone has Hemophilia A, despite their ways of inheritance, they can pass the disorder on to their offspring.

 

Sources for this page:

•  Wilson, Jennifer F., MS. "Hemophilia." Gale Encyclopedia of Medicine . Ed. Jacqueline L. Longe. 3rd ed. Detroit : Thomson Gale, 2006. Science Resource Center . Thomson Gale. 28 November 2006