In anemia, there is a reduction in the number of red blood cells in the body, or the hemoglobin in red blood cells is deficient or abnormal.
Hemoglobin is the component of red blood cells that binds with oxygen in the lungs and carries it through the circulatory system to body tissues.
If there are too few red blood cells or their hemoglobin is lacking or abnormal, the oxygen-carrying capacity of the blood is reduced and the body tissues may not receive enough oxygen.
Normally, stable hemoglobin levels in the blood are maintained by a balance between red cell production in the bone marrow and red cell destruction in the spleen. Anemia may result if this balance is upset or if the hemoglobin is abnormal. There are four main types of anemia.
The first is due to a deficiency of substances necessary for the formation of red blood cells.
The most common form of this type is iron-deficiency anemia. This is a result of low levels of iron in the body, and is most common in women who have heavy menstrual bleeding.
The second type of anemia results from inherited disorders in which abnormal hemoglobin is produced, such as in sickle cell disease ).
The third type of anemia, known as hemolytic anemia, occurs when red blood cells are broken down more rapidly than they can be replaced. This may be caused by the body’s immune system destroying red blood cells, by certain inherited disorders, or by infections such as malaria. The fourth type of anemia, called aplastic anemia, is caused by failure of the bone marrow to produce enough red blood cells.
The underlying cause is often unknown, but it may sometimes be due to toxins, radiation, or certain drug
