Myelodysplastic Syndrome (MDS) is a clonal disease that occurs due to various genetic mutations. As in many cancers, it is often a combination of genetic mutations and changes that trigger the disease. There are several forms of MDS, but many are characterized by anemia, one or more other cytopenias, and dysplasia. The anemia is often accompanied by macrocytosis; in fact, macrocytic cells can often be seen several years before the full disease manifests itself. Because the developing RBCs in the bone marrow are dysplastic, many die in the bone marrow leading to anemia.
In MDS, other cytopenias (e.g., neutropenia or thrombocytopenia) occur along with the anemia, along with the fact that there is a great deal of poikilocytosis (variation in shape) and anisocytosis (variation in size). Many times, in addition to an MCV >100 fL, an elevated RDW can also be seen.
