GSTM1 and hemoglobinopathy: Rare anemias include hemolytic anemias, such as hemoglobinopathies that are caused by inherited defects either in the structure of hemoglobin (Hb) (e.g., sickle cell disease), or in Hb synthesis (beta-thalassemia), spherocytosis that arises due to mutations in proteins responsible for the regular shape of erythrocytes or metabolic deficiencies (e.g., in glucose-6-phosphate hydrogenase) that increase oxidative stress in erythrocytes.