Fanconi Anemia Health Article

Definition

Fanconi anemia is an inherited disorder characterized by a severe form of anemia and various other physical malformations. Patients with Fanconi anemia are susceptible to various types of cancer.

Description

Fanconi anemia (FA) was first described in 1927 by a Swiss pediatrician named Guido Fanconi. It is a rare, inherited form of aplastic anemia. Aplastic anemia is a life-threatening condition in which a person is unable to produce adequate amounts of red blood cells, white blood cells, or platelets. Red blood cells serve to carry oxygen to all areas of the body. White blood cells help to fight infection and disease. Platelets are responsible for clotting to help to heal wounds and control bleeding. Without adequate amounts of these important blood cells, patients affected with aplastic anemia are easily fatigued and susceptible to infections. Most cases of aplastic anemia develop throughout the course of a person's lifetime. However, in FA, the aplastic anemia is inherited, or present from birth.

FA is also associated with various other findings. These include short stature, skeletal abnormalities, kidney problems, and heart defects. Additionally, people with FA experience a high incidence of leukemia and an increased incidence of other types of cancer.

The chromosomes in the cells of FA patients break and rearrange easily. Chromosomes are the information manuals of our cells. Genes are arranged on chromosomes in a linear fashion, like beads are arranged on a string. Genes tell our cells how to make proteins. These proteins perform many vital functions in the body. When chromosomes break, genes are disrupted and they do not function correctly. This leads to abnormal proteins and various health problems. The chromosome breakage in FA can be seen in the laboratory and is used to diagnose the disorder.

Genetic profile

It has been determined that at least eight different genes are associated with FA. A change in any one of these genes causes the disorder. The proteins made by these genes are not yet known and their role in FA is not yet understood.

For someone to be affected with FA, each of their parents must have a defect in the same gene. Parents that carry the defective gene do not show symptoms of FA because they have a corresponding gene on the other chromosome that produces an adequate amount of protein. Thus, they often do not know they are carriers until they have an affected child. If both parents carry the same defective gene, each pregnancy has a 25% chance of inheriting both abnormal genes and being affected with FA. Likewise, each pregnancy has a 25% chance of inheriting two functional copies of the gene and being unaffected. This leaves a 50% chance that the pregnancy will have one functional gene and one defective gene and will be an unaffected carrier of the disorder. This pattern is known as autosomal recessive inheritance.

The FA genes are designated by a letter of the alphabet. Defects in the FA-A gene account for approximately 65% of FA cases. Defects in the FA-C gene account for about 15% of FA cases. In the Ashkenazi Jewish population, however, defects in this particular gene are responsible for nearly all cases of FA.