Chapter 9: Iron-Deficiency Anemia and Iron Overload

INTRODUCTION

• Iron deficiency is one of the most common chronic maladies in humans. One-third to one-half of healthy females of reproductive age in the United States have absent iron stores, and 10 percent have iron deficiency anemia, also common in infants and adolescents.

• Iron overload denotes an excess of iron in the body.

DEVELOPMENTAL STAGES OF IRON DEFICIENCY

• Iron depletion: storage iron decreased or absent.

• Iron deficiency: storage iron decreased or absent with low serum iron concentration and transferrin saturation.

• Iron-deficiency anemia: storage iron decreased or absent, low serum iron concentration and transferrin saturation, and low hemoglobin level.

CAUSES OF IRON DEFICIENCY

• Chronic blood loss.

• Diversion of maternal iron to fetus/infant during pregnancy/lactation.

• Inadequate dietary intake of iron, primarily in infants and children.

• Malabsorption of iron.

• Intravascular hemolysis with hemoglobinuria.

• Combinations of the above.

Dietary Causes

• Infants most often develop iron deficiency because milk is a poor source of dietary iron and the requirements for iron imposed by rapid growth are not satisfied.

• In children, poor dietary intake plus intestinal parasites and/or bleeding gastrointestinal lesions are the usual causes.

• In the United States, average iron intake is 5 to 7 mg/day. Children and menstruating women are in precarious iron balance and at risk for iron deficiency.

Malabsorption

• Iron absorption is decreased in the malabsorption syndromes.

• After subtotal gastrectomy, malabsorption of dietary iron occurs in 50 percent of patients because of rapid gastrointestinal transit and because food bypasses the site of maximal absorption due to location of anastomosis. In contrast, medicinal iron is well absorbed after partial gastrectomy.

• In postgastrectomy anemia, there may be bleeding from anastomotic ulcer(s).

Chronic Blood Loss

• Menorrhagia is the most common cause of iron deficiency in women.

• Chronic blood loss may occur from the respiratory, gastrointestinal, or genitourinary tracts, or from phlebotomy for blood donation or laboratory testing, or it may be self-induced.

• The most common cause of iron deficiency in men and postmenopausal women is gastrointestinal bleeding.

Pregnancy and Lactation

• The average iron loss from transfer to the fetus and blood in the placenta is 900 mg. Lactation losses of iron average 30 mg/mo.

PATHOGENESIS

• Lack of iron interferes with heme synthesis, which leads to reduced hemoglobin synthesis and defective erythropoiesis.

• There is decreased activity of iron-containing enzymes, such as the cytochromes and succinic dehydrogenase.

• Neurologic dysfunction may occur, with impaired intellectual performance, paresthesias, etc.

• Impaired performance during physical exertion is often present, especially in children and young adults.

• Atrophy of oral and gastrointestinal mucosa may occur, although this is unusual except in severe prolonged deficiency.

• Gastric acid secretion may be reduced, often irreversibly.

CLINICAL FEATURES