<prompt> Microcytosis is seen in -ThalassemiaHb LeporeHb bartsAll of the above  <response>: Causes of microcytosis MCV 80fl Iron deficiency anemia Thalassemia Sideroblastic anemia Anemia of chronic diseaseIn Hb Barts, all the four a chain genes are deleted resulting in formation of Barts Hb.In Hb Lepore, there is nonhomologus fusion of b and d genes and forms an abnormal hemoglobin with total absence of normal b chain. It is one of the form of b thalassemia minor. 