Clinical Importance of Treating Iron Overload in Sickle Cell Disease

Hypothesis: The investigators suspect that significant degrees of iron overload in subjects with SCD result in decreased red cell survival, abnormal endothelial function and markedly dysregulated autonomic function. Furthermore, the investigators anticipate that the magnitude of these effects is proportional not only to the magnitude of total body iron stores but also to the duration of exposure to the high iron levels in tissues. Primary objective To determine if red cell survival as assessed by 51Cr red cell survival analysis, hemoglobin level, reticulocyte count, lactic acid dehydrogenase, and plasma hemoglobin in sickle cell patients is related to the degree of iron overload. Secondary objective(s) 1. Determine if the magnitude of endothelial-dependant vasodilation is related to The degree of iron overload. 2. Determine if the degree of change in cardiac beat to beat variability in response to hypoxic exposure or to cold exposure ("cold-face-test") is related the magnitude of iron overload. The primary measure of iron overload will be MRI determination of liver iron concentration.