Improvement of sickle cell anemia by iron-limited erythropoiesis

Abstract

We report the hematologic and clinical features of four adult patients (Pts.) with sickle cell anemia and iron-limited erythropoiesis. Two of the Pts. had spontaneous iron deficiency (chronic GI bleeding, low-grade hemoglobinuria). In the other two Pts. iron restriction was induced by periodic RBC aphereses as part of a pilot protocol designed to decrease intracellular HbS polymerization by MCHC reduction. Iron-limited erythropoiesis was defined by reduction in red cell indices (MCV range 60.4-67 fl) in the presence of low serum ferritin (range < 10-20 ng/ml). In these Pts. iron restriction did not cause clinically significant worsening of the anemia (Hb 7.8-9.0 g/dl). In two Pts. the anemia actually improved. Other hematologic effects of iron restriction were: decreased MCHC, reticulocyte count, RDW, and dense cells. A reduced hemolytic rate was suggested by a lowering of serum bilirubin and LDH. In one of the Pts. the 51Cr RBC T1/2 survival increased from 12 to 16 days. The intracellular HbS polymer fractions (fp) were determined at 25% O2 by Csat and with the use of the conservation of mass equation. The baseline fp values ranged from 0.48-0.53. After iron restriction they ranged from 0.33-0.48. The fp decreased even though iron-limited erythropoiesis also lowered the Hb F concentration in three of our Pts. In one of the two Pts. with induced iron depletion, hospitalization days for pain crises decreased from an average of 4.5 days/month (2 year baseline period) to an average of 0.5 days/month in the 3 year follow-up after iron depletion. The second patient with induced iron restriction experienced the rapid healing of a leg ulcer. Controlled iron restriction should be explored as a therapeutic strategy in selected SS patients.