Iron deficiency anemia overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

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.

Historical Perspective

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.

Causes

Iron deficiency anemia causes can be broadly divided into physiological causes as that seen during growth and pregnancy and due to pathological process. The pathological process could be further divided based on blood loss and inadequate iron absorption.

Differentiating Iron Deficiency Anemia from other Diseases

Iron deficiency anemia and Thalassemia Minor present with many of the same lab results. It is very important not to treat a patient with Thalassemia with an iron supplement as this can lead to hemochromatosis (accumulation of iron in the liver) A hemoglobin electrophoresis would provide useful evidence in distinguishing these two conditions, along with iron studies.

Epidemiology and Demographics

In the United States, the prevalence and severity of anemia have declined in recent years; hence, the proportion of anemia due to causes other than iron deficiency has increased substantially. As a consequence, the effectiveness of anemia screening for iron deficiency has decreased in the United States .

Diagnosis

History and Symptoms

Symptoms of iron deficiency are not unique to iron deficiency (i.e. not pathognomonic). Iron is needed for many enzymes to function normally, so a wide range of symptoms may eventually emerge, either as the secondary result of the anemia, or as other primary results of iron deficiency. Iron deficiency represents a spectrum ranging from iron depletion, which causes no physiological impairments, to iron-deficiency anemia, which affects the functioning of several organ systems.

Laboratory Findings

Iron status can be assessed through several laboratory tests. Since, each test assesses a different aspect of iron metabolism, results of one test may not always agree with results of other tests. Hematological tests based on characteristics of red blood cells (i.e., Hb concentration, hematocrit, mean cell volume, and red blood celldistribution width) are generally more available and less expensive than are biochemical tests. Biochemical tests (i.e., erythrocyte protoporphyrin concentration, serum ferritin concentration, and transferrin saturation), however, detect earlier changes in iron status. Except for Total iron binding capacity TIBC, transferrin saturation, and soluble transferrin receptor all other components of iron study are decreased in iron deficiency anemia. The soluble transferrin receptor test is a newer test and is found useful in distinguishing iron deficiency anemia from anemia of chronic disease.