Pernicious anemia is a special form of anemia that is the primary cause of a vitamin B12 deficiency. Pernicious anemia occurs at the end stage of an autoimmune disorder that causes the loss of various cells in the stomach. The most common cause of the vitamin B12 deficiency seen with pernicious anemia is lack of a protein called intrinsic factor, which is normally secreted by these particular cells in the stomach. Intrinsic factor binds to vitamin B12 and aids its absorption in the small intestine. Pernicious anemia results from a reduction or complete cessation of intrinsic factor production. Without intrinsic factor, vitamin B12 cannot cross the intestinal lining. Symptoms of pernicious anemia include pale skin, reduced energy and exercise tolerance, fatigue, and shortness of breath. In addition, because nerve cells are destroyed, patients with this condition lose the ability to perform coordinated movements and maintain their body's positioning. Central nervous system involvement can lead to irritability, confusion, depression, and even paranoia.
In contrast, macrocytic anemia results from a severe folate deficiency. Folate deficiency impairs DNA synthesis, which impairs the normal production of red blood cells. Macrocytic anemia is manifested as the production of larger than normal red blood cells containing insufficient hemoglobin, thus inhibiting adequate transport of oxygen. Because larger than normal red blood cells are produced in this situation, another term for macrocytic anemia is megaloblastic anemia. Symptoms of macrocytic anemia are similar to the symptoms that occur with pernicious anemia and include weakness, fatigue, difficulty concentrating, irritability, headache, shortness of breath, and reduced exercise tolerance.
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