Bone marrow - erythroid hyperplasia with dyserythropoiesis. Stainable iron is increased and a rare ringed sideroblast may be seen. There are four genes coding for alpha chain production. These genes are located on chromosome 6. As a result there are at least five forms of alpha thalassemia depending on the number and location of the abnormal genes.
All genes are abnormal.
There is no alpha chain production hence no Hgb F production and death in utero. Bart's which consists of 4 gamma chains. Hemoglobin H Disease Three genes are abnormal and one gene is coding for alpha chains. As a result there is limited production of Hgb F in utero and Hgb A after birth. The excess gamma chains form Hgb Bart's and the excess beta chains form Hgb H both of which are unstable and precipitate in the cell resulting in the premature destruction in the marrow and spleen with splenomegaly.