1. All normal erythroblasts contain some iron in the ferritin form. It may be present in either a dispersed state or in compact clusters. When large enough, these clusters may be observed in the optical microscope: they are the granular particles of the siderocytes.
2. Iron can be found in the mitochondria. It may exist either in the form of ferritin granules or as ferruginous micelles.
3. In thalassemia, large quantities of iron accumulate in the erythroblasts and are even found in the erythrocytes as ferritin, in cluster formation or dispersed. Occasionally, iron is present in great quantities in the mitochondria as ferritin or micelles. It seems that the various disorders encountered in thalassemia may thus be ascertained; the disturbance in hemoglobin synthesis results in the accumulation of the unused iron in the hypochromic erythrocytes.
4. In diseases very similar to thalassemia and in which no fetal hemoglobin is found, i.e., the hypochromic-hypersideremic anemias (sidero-achestic anemia, hypochromic hypersideremic anemia, lead-poisoning ), similar findings are observed.
5. Normally, it is probable that iron metabolism occurs in the mitochondria. In thalassemia and hypochromic hypersideremic anemias, on the other hand, iron metabolism often appears to be "blocked" in the same areas.