Hemoglobin Types and Variants

Posted by ThirdAge Editorial Staff on April 30, 2010 5:23 PM

Hemoglobin variants are abnormal forms of hemoglobin, an iron-containing protein molecule found in all red blood cells. Hemoglobin binds oxygen in the lungs, carries oxygen from the lungs throughout the body, and releases oxygen to the body's cells and tissues. Hemoglobin variants occur when there are genetic changes in the globin genes, affecting the structure, the behavior, the stability and/or the production rate of the hemoglobin.

Normal Hemoglobin Types

Normal hemoglobin types found in our body include Hb A, Hb A2 and Hb F. Hb A composes about 95 to 98 percent of Hb found in your body and contains two alpha protein chains and two beta protein chains. Hb A2 makes up a smaller portion -- about 2 percent -- of the Hb in your body. It has two alpha and two delta protein chains. Hb F makes up 2 percent of the Hb found in your body. It has two alpha and two gamma protein chains.

Variant Hemoglobin Types

Variants in a person's hemoglobin can occur when there are genetic changes in the globin genes. There are four common hemoglobin variants. Hemoglobin S (Hb S) is the primary hemoglobin in those with sickle cell disease. Hb S causes the red blood cells to deform due to decreased amounts of oxygen, turning the red blood cells into a sickle shape. This shape instigates blockages in the small blood vessels, causing extreme pain, reduced circulation, decreased oxygen-carrying capacity of the red blood cells, and a decreased lifespan for the red blood cells.

Hb C is a rare a relatively mild hemoglobin variant. It can cause a mild to moderate enlargement of the spleen as well as hemolytic anemia, an anemia problem causing red blood cells to die prematurely.Hemoglobin E (Hb E) is the most common beta chain hemoglobin variant. People with Hb E typically have microcytic red blood cells, mild enlargement of the spleen and mild hemolytic anemia.While there have been several hundred beta hemoglobin variant chains documented by scientists, only a few are common. Many variants cause no signs or symptoms, while others affect the function and stability of hemoglobin.