When iron cannot be properly incorporated into heme, or insufficient heme is produced, the iron will accumulate in mitochondria around the nucleus of the erythroblast. The image shows Prussian blue staining of the mitochondrial iron. This defect may be seen in a variety of disorders, such as congenital deficiency of heme production, exposure to mitochondrial toxins such as lead or alcohol, or in myelodysplastic syndromes--indeed an increase of ringed sideroblasts is one of the defining features for "MDS-refractory anemia with ringed sideroblasts." The resulting anemia is typically microcytic and hypochromic.
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