Genetic blood diseases are the result of DNA mutations that have spread throughout a population via genetic inheritance. These disorders can cause problems ranging from excessive bleeding to an inability of the blood to efficiently carry oxygen.
Hemophilia
People with hemophilia have blood that does not clot properly, due to defects or the absence of clotting factors in their blood. This results in excessive bleeding from wounds. There are 13 different clotting factors designated by the Roman numerals I through XIII. Different versions of hemophilia are the result of defects in the genes that produce the different clotting factors. The most common versions are Hemophilia A, the result of a missing or damaged clotting factor VIII, and Hemophilia B, which occurs when clotting factor IX is not produced or is produced in small amounts. Because the clotting factors are located on the X chromosome, males are affected more frequently than females. If a male's single X chromosome is damaged, there is no backup gene on another X chromosome, as is the case in females.
Thalassemia
Thalassemia affects about 1,000 people in the United States and is the result of a genetic defect in red blood cells that limits their ability to produce hemoglobin, the compound that allows those cells to carry oxygen to tissues. There are several forms of thalassemia, with the most serious being Cooley's Anemia. People with thalassemia exhibit debilitating anemia starting in childhood and often need blood transfusions throughout their lives.
Von Willebrand Disease
The genetic disorder von Willebrand Disease (vWD) is the most common inherited bleeding disorder, affecting 1 to 2 percent of the population. In von Willebrand disease, a blood component called von Willebrand factor is defective or absent. Von Willebrand factor carries blood factor VIII, which helps blood clot and allows wounds to heal. Type 1 vWD involves having a low level of von Willebrand factor and is often mild, sometimes going undiagnosed for years. Type 2 is the result of having abnormal von Willebrand factor and people with type 3 vWD have very low or nonexistent levels of von Willebrand factor. Pseudo von Willebrand disease, also called platelet-type vWD, is the result of abnormal platlets that cling to von Willebrand factor, limiting its activity.
Sickle Cell Anemia
In sickle cell anemia, hemoglobin is malformed, causing the red blood cells to change into a form that looks like a sickle or crescent. These cells cling together and stick to the walls of blood vessels, preventing the cells from carrying oxygen to where it is needed. These sickle cells break down more rapidly than normal red blood cells, resulting in anemia. People with sickle cell anemia also exhibit jaundice and experience extreme pain at times. When a person has a single sickle cell gene only half of their blood cells are affected, allowing them to function normally. Inheriting the sickle cell gene from both parents causes the full-blown disorder. Sickle cell anemia mostly affects people of African ancestry, with 1 in 12 African-Americans being carriers of one copy of the sickle cell gene.
