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INTRODUCTION

SUMMARY

The anemia that results from deficiencies of vitamin B12, folic acid (Chap. 42), or iron (Chap. 44) are, in general, clearly defined and are relatively common. In contrast, the characteristics of anemia that may occur with deficiencies of other micronutrients, such as some of the other vitamins and minerals, are poorly defined and relatively rare in humans. When present, they usually exist not as isolated deficiencies of one vitamin or one mineral but rather as a combination of deficiencies resulting from malnutrition or malabsorption. In this context, it is difficult to deduce which abnormalities are a result of which deficiency. Studies in experimental animals may not accurately reflect the role of micronutrients in humans. Accordingly, our knowledge of the effect of many micronutrients on hematopoiesis is fragmentary and based on clinical observations and interpretations that may be flawed. Inborn metabolic errors that affect single micronutrient pathways may shed light on the specific effects of those micronutrients on hematopoiesis. The levels normally found in the serum, red cell, and leukocytes are shown in Table 45–1.

Acronyms and Abbreviations

MCV, mean corpuscular volume; RDW, red cell distribution width.

TABLE 45–1.Blood Vitamin and Mineral Levels (Adult Values)

VITAMIN-DEFICIENCY ANEMIAS

VITAMIN A DEFICIENCY

Chronic deprivation of vitamin A results in anemia similar to that observed in iron deficiency.1–4

Mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) are reduced. Anisocytosis and poikilocytosis may be present, and serum iron levels are low. Unlike iron-deficiency anemia but similar to the anemia of chronic disease, the iron stores in the liver and marrow are increased, the serum transferrin concentration usually is normal or decreased, and administration of medicinal iron does not correct the anemia. However, there is evidence to indicate that vitamin A deficiency may result in impaired iron absorption or utilization5 and that this may be mediated through effects on expression of genes involved in the regulation of intestinal iron absorption.6 The suggestion that vitamin A may facilitate iron absorption7 has not been confirmed.8 Supplementation with vitamin A alone may ameliorate the ...

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