Silent Infarct Transfusion Trial (SITT)

eligible subjects who have sickle cell disease will undergo a screening MRi of the brain and transcranial Doppler ultrasonography (TCD). Those who have [Quote]silent infarcts[Quote] on MRi and no increased risk of overt stroke (determined by TCD) may then be randomized to receive either red blood cell transfusions (preferably by erythrocytapheresis, alternatively by simple transfusion) or observation for 3 years. The primary outcome, the occurrence of new silent or overt stroke, will be determined by serial physical examinations and MRi of the brain. neuropsychological testing will be completed on all subjects to assess their learning, thinking, and memory abilities over time. Subjects and their families will undergo multiple education sessions in which the alternatives to and the implications of the study will be presented and discussed. Subjects will also participate in genetic studies to determine associations between genetic polymorphisms and stroke (or absence of stroke). Blood (plasma) will also be obtained at certain visits on some of the participants to study proteins and other factors associated with strokes or sickle cell severity.