Cerebrovascular Reserve and White Matter Disease in Patients with Chronic Anemia

This is primarily an observational trial in patients with chronic anemia syndromes (sickle cell disease and thalassemia) and control subjects. The key purpose is to understand how brain blood flow reserve (the ability of the brain to increase its flow in response to stress) is altered in patients with chronic anemia. Since this parameter may depend on anemia severity, we will perform the MRI monitoring prior to and following clinically indicated transfusions in a subset of patients. Most patients will already be prescribed hydroxyurea as part of their standard of care. Since hydroxyurea could impact brain blood flow, there is also a small pilot study (20 patients, nonrandomized, open label) where MRI imaging will be performed prior to and following administration of hydroxyurea up to maximum tolerated dose. The study will enroll 90 adult subjects with transfusion independent sickle cell disease (70 SS, 10 SC, 10 Sβ0) and 60 patients with transfusion-dependent sickle cell disease. It will also include 10 transfusion independent thalassemia patients and 20 transfusion dependent thalassemia patients as well as 40 control subjects recruited from first degree relatives of the sickle cell disease population. All eligible subjects will be asked to provide informed consent before participating in the study.