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Iron deficiency anemia is the most common type of anemia, and the most common cause of microcytic anemia.
Iron deficiency anemia occurs when the dietary intake or absorption of iron is insufficient, and hemoglobin, which contains iron, cannot be formed. In the United States, 20% of all women of childbearing age have iron deficiency anemia, compared with only 2% of adult men. The principal cause of iron deficiency anemia in premenopausal women is blood lost during menses.
Iron deficiency anemia is the final stage of iron deficiency. When the body has sufficient iron to meet its needs (functional iron), the remainder is stored for later use in the bone marrow, liver, and spleen. Iron deficiency ranges from iron depletion, which yields little physiological damage, to iron deficiency anemia, which can affect the function of numerous organ systems. Iron depletion causes the amount of stored iron to be reduced, but has no effect on the functional iron. However, a person with no stored iron has no reserves to use if the body requires more iron. In essence, the amount of iron absorbed by the body is not adequate for growth and development or to replace the amount lost.
History
A disease believed to be iron deficiency anemia is described in about 1500 B.C. in the Egyptian Ebers papyrus. It was termed chlorosis or green sickness in Medieval Europe, and iron salts were used for treatment in France by the mid-17th century. Thomas Sydenham recommended iron salts as treatment for chlorosis, but treatment with iron was controversial until the 20th century, when its mechanism of action was more fully elucidated.
Symptoms
Iron deficiency anemia is characterized by pallor, fatigue and weakness. Because it tends to develop slowly, adaptation occurs and the disease often goes unrecognized for some time. In severe cases, dyspnea can occur. Unusual obsessive food cravings, known as pica, may develop. These may include ice, cake mix, laundry starch, and dirt.
Diagnosis
Anemia will be diagnosed on the basis of suggestive symptoms, or found on the basis of routine testing, which includes a complete blood count (CBC). A sufficiently low hemoglobin or hematocrit value is diagnostic of anemia, and further studies will be undertaken to determine its cause. One of the first abnormal values to be noted on a CBC will be a high red blood cell distribution width (RDW), reflecting a varied population of red blood cells. A low MCV, MCH or MCHC, and the appearance of the RBCs on visual examination of a peripheral blood smear will narrow the diagnosis to a microcytic anemia.
The diagnosis of iron deficiency anemia will be suggested by appropriate history (e.g., anemia in a menstruating woman), and by such diagnostic tests as a low serum ferritin, a low serum iron level, an elevated serum transferrin and a high total iron binding capacity (TIBC). A definitive diagnosis requires a demonstration of depleted body iron stores by performing a bone marrow aspiration, with the marrow stained for iron. Because this is invasive and painful, while a clinical trial of iron supplementation is inexpensive and non-traumatic, patients are often treated without a definitive diagnosis.
The diagnosis of iron deficiency anemia requires further investigation as to its cause. It can be a sign of other disease, such as colon cancer, which will cause the loss of blood in the stool. In addition to dietary insufficiency, malabsorption, chronic blood loss, diversion of iron to fetal erythropoiesis during pregnancy, intravascular hemolysis and hemoglobinuria or other forms of chronic blood loss should all be considered.
Treatment
If the cause is dietary iron deficiency, iron supplements, usually with iron (II) sulfate or iron amino acid chelate, can correct the anemia. Chelated iron, while not as widely known as iron sulfate, is ten to fifteen times more bioavailable per mg and has none of the side effects of iron sulfate's sulfur content. Iron supplements must be kept out of the reach of children, as iron-containing supplements are a frequent cause of poisoning in the pediatric age group. If malabsorption is present, it may be necessary to administer iron parenterally (e.g., as iron dextran). Parenteral iron other than in chelated form, however, is generally poorly tolerated.
Follow up evalution with CBC is essential to demonstrate whether the treatment has been effective.
"Iron deficiency anemia"