Prevention. Bottle-fed infants should receive an iron-containing formula until 12 months of age, and breastfed infants older than 6 months of age should receive an iron supplement. The introduction of iron-enriched solid foods at 6 months of age, followed by a transition to a limited amount of cow’s milk and increased solid foods at 1 year, can help prevent iron deficiency anemia. Teenage girls who are menstruating should have a diet enriched with iron-containing foods. A vitamin with iron may also be used.
Etiology and Epidemiology. α-Thalassemia and β-thalassemia minor are common causes of microcytosis, either with or without a mild hypochromic, microcytic anemia. They are prevalent in certain ethnic groups (Mediterranean, Southeast Asian, African Americans). Individuals of Asian descent are at risk of having three or four α genes deleted, resulting in hemoglobin H disease (γ4) or hydrops fetalis with only Bart (α4) hemoglobin (Table 150-5 and Fig. 150-3).
Laboratory Testing. The thalassemia minor syndromes are characterized by a mild hypochromic, microcytic anemia with a low absolute reticulocyte count (see Table 150-5). The RBC count is usually elevated. As a result, if the mean corpuscular volume (MCV) divided by the RBC count is less than 12.5 (Mentzer index), the diagnosis is suggestive of thalassemia trait. The blood smear reveals only microcytosis with α-thalassemia trait. Outside the neonatal period, when Bart hemoglobin is detectable, hemoglobin electrophoresis usually is normal in α-thalassemia minor (see Fig. 150-3). Blood smears of patients with β-thalassemia minor show microcytic RBCs. Target cells and basophilic stippled RBCs, caused by precipitation of alpha chain tetramers, also may be present. The diagnosis is based on an elevation of hemoglobin A2 and F levels in β-thalassemia. Molecular testing is indicated for identification of more severe or unusual variants.
Treatment. No treatment is required for children with thalassemia minor. However, children with hemoglobin H disease (γ4), especially the Constant Spring variant or hydrops fetalis with only Bart (α4) hemoglobin, are likely to require chronic transfusion therapy.
Lead poisoning may be associated with a hypochromic, microcytic anemia. Most patients have concomitant iron deficiency. The history of living in an older home (built before 1980) with chipped paint or lead dust should raise suspicion of lead poisoning, especially in a child with pica. Basophilic stippling on the blood smear is common. Lead intoxication
Table 150-5 Thalassemia Syndromes DISORDER GENOTYPIC ABNORMALITY CLINICAL PHENOTYPE β-THALASSEMIA Thalassemia major (Cooley’s anemia) Homozygous β0-thalassemia Severe hemolysis, ineffective erythropoiesis, transfusion dependency, hepatosplenomegaly, iron overload
Thalassemia intermedia Compound heterozygous β0and β+-thalassemia Moderate hemolysis, splenomegaly, moderately severe anemia, but not transfusion-dependent; main life-threatening complication is iron overload
Thalassemia minor Heterozygous β0and β+-thalassemia Microcytosis, mild anemia
Hydrops fetalis -/-Severe anemia, intrauterine anasarca from congestive heart failure; death in utero or at birth
From Andreoli T, Carpenter C, Griggs R, et al: Cecil Essentials of Medicine, ed 7, Philadelphia, 2007, Saunders.
*The Constant Spring variant may require chronic transfusion.