The red blood cell distribution width (RDW) increases as the severity of alpha thalassemia increases...

The red blood cell distribution width (RDW) increases as the severity of alpha thalassemia increases because of changing MCV as the bone marrow produces smaller cells. In addition, if Hemoglobin H bodies are present, they result in the formation of schiztocytes (RBC fragments) that can have an effect on the MCV and RDW.

The Red cell Distribution Width (RDW) in alpha thalassemia is