Epidemiology. The prevalence of iron deficiency, the most common cause of anemia in the world, is about 9% in toddlers, 9% to 11% in adolescent girls, and less than 1% in teenage boys. Iron deficiency anemia occurs in about one third of children who are iron deficient (Table 150-3). Some underprivileged minority populations in the United States may be at increased risk for iron deficiency because of poor dietary intake (see Chapter 31). Breastfed infants are less likely to have iron deficiency than bottle-fed infants because, although there is less iron in breast milk, this iron is more efficiently absorbed.
Clinical Manifestations. In addition to cardiovascular manifestations of anemia, central nervous system (CNS) abnormalities (apathy, irritability, poor concentration)have been linked to iron deficiency, presumably resulting from alterations of iron-containing enzymes (monoamine oxidase) and cytochromes. Poor muscle endurance, gastrointestinal dysfunction, and impaired WBC and T-cell function have been associated with iron deficiency. Iron deficiency in infancy may be associated with later cognitive deficits and poor school performance.
Treatment. In an otherwise healthy child, a therapeutic trial of iron is the best diagnostic study for iron deficiency as long as the child is re-examined and a response is documented. The response to oral iron includes rapid subjective improvement, especially in neurologic function (within 24 to 48 hours) and reticulocytosis (48 to 72 hours); increase in hemoglobin levels (4 to 30 days); and repletion of iron stores (in 1 to 3 months). The usual therapeutic dose of 4 to 6 mg/day 10–12 nc/nc ↓ Fe2+ absent, erythroid hyperplasia <12 8–10 hypo/nc ↓ Fe2+ absent, erythroid hyperplasia <12 <8 hypo/micro* ↓ Fe2+ absent, erythroid hyperplasia <12
From Andreoli TE, Bennett JC, Carpenter CC, et al: Cecil Essentials of Medicine, ed 4, Philadelphia, 1997, WB Saunders. hypo/micro, Hypochromic, microcytic; hypo/nc, hypochromic, normocytic; nc/nc, normochromic, normocytic. *Microcytosis, determined by a mean corpuscular volume (in fL) <2 SD below the mean, must be adjusted for age (e.g., –2 SD at 3–6 mo = 74; at 0.5–2 yr = 70; at 2–6 yr = 75; at 6–12 yr = 77; and at 12–18 yr = 78).
*See Table 150-3 for definition of microcytosis.
†α-Thalassemia minor can be diagnosed by the presence of Bart hemoglobin on newborn screening.
‡Usually normochromic; 25% of cases are microcytic. §Red blood cell distribution width quantitates the degree of anisocytosis (different sizes) of red blood cells.
of elemental iron induces an increase in hemoglobin of 0.25 to 0.4 g/dL/day (a 1%/day increase in hematocrit). If the hemoglobin level fails to increase within 2 weeks after institution of iron treatment, careful re-evaluation for ongoing blood loss, development of infection, poor compliance, or other causes of microcytic anemia is required (Table 150-4; see Fig. 150-1).