Disorders of Erythropoiesis, Granulopoiesis and Thrombopoiesis

Bone marrow cellularity is mildly increased as a result of a moderate degree of erythroid hyperplasia. Erythropoiesis is micronormoblastic with erythroblasts being smaller than normal with scanty or ragged cytoplasm or with cytoplasmic vacuolation (Fig. 8.1). There is a minor degree of dyserythropoiesis. An iron stain shows siderotic granules to be severely reduced or absent and there is a complete or virtual absence of the iron within macrophages which usually constitutes the body’s iron stores (see Fig. 2.1). Since iron is irregularly distributed in the marrow, a number of bone marrow fragments must be available for the performance of an iron stain before it can be concluded that storage iron is lacking. In iron deficiency, the bone marrow sometimes shows occasional giant metamyelocytes but granulopoiesis and thrombopoiesis are otherwise usually normal. Individuals whose bone marrow lacks storage iron but in whom erythropoiesis is normal should be regarded as iron depleted rather than as iron deficient; a significant proportion of healthy women fall into this group. EIGHT