There is often an excess production or accumulation of globin chains in thalassemias whose genes are not affected by the deletion. In beta thalassemia, this may be seen as an increase in gamma chain and delta chain production, leading to increased levels of hemoglobin F and A2 respectively. These hemoglobins have a higher oxygen affinity, leading to decreased oxygenation of the tissues and clinical symptoms respective to this state.
In addition the excess free alpha chains produced in this condition form insoluble precipitates within the red blood cells, often causing red cell membrane damage and decreased cellular deformability. This leads to a hemolytic anemia. Adding to the anemia is a decrease in the total amount of hemoglobin produced in spite of the erythroid hyperplasia of the bone marrow.