Differential Diagnosis of Microcytic Anemia

To: Sujit Sheth (Hematology)
Date: Thu, Jun 14, 2001, 12:46 AM
Question: What is the differential diagnosis of childhood microcytic anemia?

Answer: The three most common conditions to consider when a child has microcytic anemia are:

i) Iron deficiency anemia. This may be nutritional or secondary to blood loss, and the history provides important differentiating clues. The specific studies that may confirm this diagnosis are the serum iron, the total iron binding capacity (TIBC) and the serum ferritin. The transferrin saturation equals the serum iron over the TIBC, and it is always low (less than 16%) in iron deficiency anemia, as is the serum ferritin.

ii) The thalassemia syndromes -- a or b. The diagnosis of homozygous b thalassemia is discussed elsewhere. Heterozygosity (b thalassemia trait) may be differentiated from iron deficiency by using Mentzer’s index (MCV over RBC count in millions). An index of more than 13 indicates iron deficiency, whereas less than 12 indicates the trait. Moreover, in thalassemia trait, the iron studies are usually normal, and on hemoglobin electrophoresis, there is an increase in the amount of Hgb F and Hgb A2 (greater than 3, 5%). a thalassemia trait is a diagnosis of exclusion which may be confirmed by genetic analysis of the a globin genes.

iii) Chronic lead poisoning with associated iron deficiency. A venous blood lead level is diagnostic.

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