Differential Diagnosis

Although hypochromic anemia in children is usually due to iron deficiency, it is not necessarily attributable to this condition. A list of the causes of hypochromia is given in Table 3-9. In some of these cases, there is an inability to synthesize hemoglobin normally in spite of adequate iron (e.g., thalassemia, lead poisoning). In unusual or obscure cases of hypochromic anemia, it is necessary to do additional

Table 3-8. Diagnostic Tests for Iron-Deficiency Anemia

1. Blood smear a. Hypochromic microcytic red cells, confirmed by RBC indices:

(1) MCV less than acceptable normal for age (see Appendix 1)

b. Wide red cell distribution width (RDW) greater than 14.5%

2. Free erythrocyte protoporphyrin: elevated

3. Serum ferritin: decreased

4. Serum iron and iron binding capacity a. Decreased serum iron b. Increased iron-binding capacity c. Decreased iron saturation (16% or less)

5. Therapeutic responses to oral iron a. Reticulocytosis with peak 5-10 days after institution of therapy b. Following peak reticulocytosis hemoglobin level rises on average by 0.25-0.4 g/dL/day or hematocrit rises 1%/day

6. Serum transferrin receptor level"

7. Red blood cell zinc protoporphyrin/heme ratio"

8. Bone marrow6

a. Delayed cytoplasmic maturation b. Decreased or absent stainable iron

"Rarely required or readily available.

"Used only if difficulty is experienced in elucidating cause of anemia.

investigations, such as determination of serum ferritin, serum transferrin receptor levels, hemoglobin electrophoresis, and examination of the bone marrow for stained iron, in order to establish the cause of the hypochromia.

Table 3-10 lists the investigations employed in the differential diagnosis of micro-cytic anemias and Figure 3-2 depicts a flow chart for the diagnosis of microcytic anemia using MCV and RDW.

Table 3-9. Disorders Associated with Hypochromia

1. Iron deficiency

2. Hemoglobinopathies a. Thalassemia (a and ß)

b. Hemoglobin Köln c. Hemoglobin Lepore d. Hemoglobin H

e. Hemoglobin E

3. Disorders of heme synthesis caused by a chemical a. Lead b. Pyrazinamide c. Isoniazid

4. Sideroblastic anemias (Table 6-24)

5. Chronic infections or other inflammatory states

6. Malignancy

7. Hereditary orotic aciduria

8. Hypo- or atransferrinemia Congenital

Acquired (e.g., hepatic disorders); malignant disease, protein malnutrition (decreased transferrin synthesis), nephrotic syndrome (urinary transferrin loss)

9. Copper deficiency

10. Inborn error of iron metabolism

Congenital defect of iron transport to red cells

Table 3-10. Summary of Laboratory

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