Myelodysplasia and Iron-Transport Deficiency Anemia
(See also Overview of Decreased Erythropoeisis.)
In myelodysplastic syndrome, anemia is commonly prominent. The anemia is usually normocytic or macrocytic with a dimorphic (large and small) population of circulating cells. Bone marrow examination shows decreased erythroid activity, megaloblastoid and dysplastic changes, and, sometimes, increased numbers of ringed sideroblasts. Treatment is directed at the malignancy, and growth factors are frequently used.
Iron-transport deficiency anemia (atransferrinemia) is exceedingly rare. It occurs when iron cannot move from storage sites (eg, mucosal cells, liver) to the erythropoietic precursors. One well-known form is iron-refractory iron-deficiency anemia (IRIDA), caused by germline mutations in the TMPRSS6 gene. Patients have a microcytic anemia with very low transferrin saturation and are refractory to oral iron. TMPRSS6 encodes a transmembrane protein that regulates production of hepcidin. Patients have defective hepcidin regulation, with inappropriately elevated levels despite iron deficiency.