Dimorphic is a term used to describe two circulating red cell populations. One is the patient's basic red cell population; the other is a second population with distinct morphological features. The distinct populations can be observed in the top image on the right. The bottom image on the right illustrates the two distinct peaks that are observed on the RBC histogram from the automated hematology analyzer.
Dimorphic red blood cell populations can be found in conditions/situations such as: red blood cell transfusions; myelodysplasia; refractory anemia with ringed sideroblasts; hemolytic processes involving a reticulocyte response; and erythropoietin therapy.
It is important to recognize when a population of cells in the peripheral smear is not in context with anticipated laboratory findings and the clinical situation.