Multiple: Anemias

The anemias are a group of blood disorders characterized by too little hemoglobin in the blood. Hemoglobin is a substance contained in red blood cells that carries oxygen from the lungs to other body tissues. Anemia is often a sign or symptom of an underlying disease rather than a disease in its own right. There are three tests commonly used to detect anemia: the number of red blood cells can be counted; the amount of hemoglobin in the red blood cells can be measured; or the proportion of blood cells to serum (the liquid part of blood, called the hematocrit) can be assessed.

Anemia can develop in three ways: loss of blood through injury, diseases of the digestive tract, or heavy menstrual flow in women; rapid destruction of red blood cells (for example in sickle cell anemia); or inadequate production of healthy red blood cells (for example in thalassemia). The underlying causes of anemias range from poor nutrition (iron-deficiency anemia) and digestive disorders (Crohn disease, celiac disease) to colorectal cancer, parasitic diseases (hookworm), and genetic disorders (sickle cell anemia, thalassemia).

The anemias are the most common type of blood disorder in the general population, affecting 4 percent of men and 8 percent of women in the developed countries, and two to five times as many people in the poorer nations.

SEE ALSO Celiac disease; Colorectal cancer; Crohn disease; Heart failure; Lead poisoning; Prematurity; Restless legs syndrome; Sickle cell anemia; Thalassemia; Ulcers