Red cell superoxide dismutase and sickle cell anemia symptom severity

Patients with sickle cell anemia vary in the severity of their symptoms but the basis of this variability is unknown. We have tested the hypothesis that this variability is related to differences in the activity of the antioxidant superoxide dismutase (SOD). The amount of superoxide dismutase I (SOD) enzyme activity in red cells of patients with different degrees of symptom severity and healthy black and white controls was measured and correlated with symptom severity in SCA patients. Blacks with normal (AA) hemoglobin had significantly (p less than .001) more SOD activity (1.82 U/mg Hb) than white controls (1.44 U/mg Hb). Patients with moderate or severe symptoms had less SOD activity (1.16 and 0.95 U/mg Hb, respectively) than control blacks or SCA patients with mild symptoms (1.62 U/mg Hb). The correlation of SOD activity and symptom severity was not a function of age or sex and was unrelated to reticulocyte count or fetal hemoglobin level.