Thalassemia is an inherited condition marked by iron overload due to ineffective hemoglobin production. It can be classified as alpha or beta and some individuals carry both traits. In cases like this, it may look like iron deficiency anemia, i.e. low MCV, MCH, and MCHC (i.e. a hypochromic microcytic anemia) but the iron and the ferritin are going to be quite high. In many cases of Thalassemia the RDW will be normal because, for some reason the red cells are all of the same size (RDW is a measure of the degree of variation in red cell size) it is usually elevated in Iron def anemia. However people with the alpha beta trait for thalassemia will have a much higher RDW than just the beta trait.