Thalassemia

Inheritance	autosomal recessive
Occurrence	about 100,000 babies are born every year world wide with severe forms of thalassemia (Beta thalassemia is only one of these)
Description	a defect in the beta chain of hemoglobin resulting in severe anemia
Treatment	depends on the severity; the most severe require blood transfusions every few weeks; the least severe suffer only mild anemia

Hemoglobin

We all depend on the hemoglobin found in our red blood cells to transmit oxygen throughout our bodies. Thalassemia is a type of red blood cell deficiency derived from the inability to make correct hemoglobin. In utero, a fetus produces fetal hemoglobin made of two chains-- alpha and gamma. Fetal hemoglobin has a very high affinity for oxygen and thus makes it possible to capture oxygen from the maternal hemoglobin. At birth the infant stops producing this hemoglobin and starts making adult hemoglobin made of two chains-- alpha and beta. One form of thalassemia is called alpha thalassemia. This disorder is the inability to make proper alpha chains and can affect individuals both before and after birth. Fortunately there are four genes (duplicate copies) that produce alpha chains, so in order for alpha thalassemia to be very severe, two or more of those genes have to stop production of alpha chains. If all four genes cannot make alpha chains the individual cannot produce proper fetal or adult hemoglobin. This severe form of alpha thalassemia is usually fatal before birth or shortly thereafter.

Beta thalassemia (Cooley's Anemia) affects the body's ability to make beta chains. Because beta chains are not needed before birth, a child with beta thalassemia is born perfectly normal, but as the body switches production from fetal hemoglobin to adult hemoglobin, problems result. Some individuals retain the ability to produce gamma chains and continue to produce fetal hemoglobin and do not have severe problems with their reduced beta chain production. Beta chains are formed by two different genes, and some people only have one dysfunctional gene and thus make an adequate (but not desirable) amount of hemoglobin. They suffer mild anemia but are generally OK. Individuals who cannot produce any beta chains at all have some serious problems. They are normal at birth but within several months develop severe anemia. Their bodies are producing abnormal red blood cells because of the missing beta chain in the hemoglobin. These abnormal red blood cells are quickly removed and destroyed by the spleen. This creates a deficit in oxygen supply, and so the body begins to compensate by increasing production of red blood cells. It is a devastating cycle because the new red blood cells are just destroyed by the spleen and production continues to increase. Red blood cells are made in the bone marrow found inside our bones. To increase production of red blood cells the body converts hardened bone back into spongy bone marrow. This causes weakened bones as well as severe deformities. For many individuals, broken bones is a recurring problem. Without treatment this cycle continues until death results. The only available treatment is blood transfusions every few weeks. This provides the individual with functioning donor red blood cells. This treatment is costly, dangerous (because of the high volumes of blood needed every few weeks, risk of infection is higher), and has one additional huge problem. Our bodies recycle and do not get rid of iron. As the donor red blood cells are destroyed the iron is recycled. This causes a build up of iron in the body. Ultimately this condition can cause death as individuals develop iron overload and iron poisoning.

Many new treatments are being developed to reduce the levels of iron in the body. One of the most successful new treatments is an iron chelator that causes iron to be excreted in the urine. This treatment requires a subcutaneous infusion of a drug every night for about twelve hours. It is painful and tedious, but does slow the build up of iron in the body.

Beta thalassemia can be discussed when learning about red blood cells, hemoglobin, blood production, and iron. It can be incorporated into a variety of units and topics. One way to introduce this is to have students research hemoglobin or thalassemia. It is also appropriate to discuss under nutrition. An interesting side note is that most normal men will never suffer from anemia (lack of iron) whereas women will. This is due to the fact that the only way to reduce the levels of iron in the body is through bleeding. Women lose blood every month due to menstruation and thus always need to replenish their iron through diet and/or vitamins. Men do not lose blood on any regular basis and generally never have that problem.

Beta Thalassemia (Cooley's Anemia)

Hemoglobin