Iron deficiency anemia
With iron deficiency anemia, an inadequate supply of iron for optimal formation of red blood cells (RBCs) results in smaller (microcytic) cells with less color on staining. Body stores of iron, including plasma iron, decrease, as does transferrin, which binds with and transports iron. Insufficient body stores of iron lead to a depleted RBC mass and, in turn, a decreased hemoglobin (Hb) level (hypochromia) and decreased oxygen-carrying capacity of the blood. A common disease worldwide, iron deficiency anemia affects 10% to 30% of adults in the United States.
Causes
Iron deficiency anemia may result from:
inadequate dietary intake of iron (less than 2 mg/day)—for example, during prolonged, unsupplemented periods of breast- or bottle-feeding (not eating solid foods after age 6 months) and during periods of stress, such as rapid growth in children and adolescents
iron malabsorption, as in chronic diarrhea, partial or total gastrectomy, and malabsorption syndromes such as celiac disease
blood loss secondary to drug-induced GI bleeding (from anticoagulants,
aspirin, or steroids) or due to heavy menses, hemorrhage from trauma, a GI ulcer, cancer, or bleeding varices
pregnancy, which diverts maternal iron to the fetus for erythropoiesis
intravascular hemolysis-induced hemoglobinuria or paroxysmal nocturnal hemoglobinuria
mechanical erythrocyte trauma caused by a prosthetic heart valve or vena cava filters.
Iron deficiency anemia is most common in premenopausal women, infants (particularly premature and low-birth-weight infants), children, and adolescents (especially girls).
Signs and symptoms
Because of the gradual progression of iron deficiency anemia, many patients are initially asymptomatic. They tend not to seek medical treatment until anemia is severe.
At advanced stages, a decreased Hb level and the consequent decrease in the blood’s oxygen-carrying capacity cause the patient to develop exertional dyspnea, fatigue, listlessness, pallor, inability to concentrate, irritability, headache, and a susceptibility to infection. Decreased oxygen perfusion causes the heart to compensate with increased cardiac output and tachycardia.
With chronic iron deficiency anemia, nails become spoon shaped and brittle, the corners of the mouth crack, the tongue turns smooth, and the patient complains of dysphagia or may develop pica. Associated neuromuscular effects include vasomotor disturbances, numbness and tingling of the extremities, and neuralgic pain.
Diagnosis
Blood studies (serum iron, total iron-binding capacity, and ferritin levels) and stores in bone marrow may confirm iron deficiency anemia. However, the results of these tests can be misleading because of complicating factors, such as infection, pneumonia, blood transfusion, and iron supplements. Characteristic blood study results include:
low Hb levels (males, less than 12 g/dl; females, less than 10 g/dl)
low hematocrit (males, less than 47 ml/dl; females, less than 42 ml/dl)
low serum iron levels, with high iron-binding capacity
low serum ferritin levels
low RBC count, with microcytic and hypochromic cells (in early stages, RBC count may be normal, except in infants and children)
decreased mean corpuscular Hb level (in patients with severe anemia).
Bone marrow studies reveal depleted or absent iron stores (done by staining) and normoblastic hyperplasia.
The diagnosis must rule out other forms of anemia, such as those that result from thalassemia minor, cancer, and chronic inflammatory, liver, and kidney disease.
