A Prussian Blue histochemical stain of a bone marrow aspirate of a patient with myelodysplastic disorder, refractory anemia with ringed sideroblasts, is shown. Abnormal accumulation of iron in the mitochondria of the late erythroid precursor cells can be seen. Ringed sideroblasts can also be seen in hereditary sideroblastic anemia and number of acquired conditions including lead and zinc poisoning, and drugs including chloramphenicol and isoniazid, and in copper deficiency.