A 23-year-old African American woman with homozygous hemoglobin SS (HbSS) disease presents to initiate care. She has been on monthly simple transfusion therapy since she was found to have a transcranial Doppler (TCD) velocity of 220 cm/sec in her right middle cerebral artery at age 7 years. She has not had an overt stroke, and her last magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) evaluation, at age 16, was negative for moyamoya or significant stenosis. There were mild ischemic changes in the frontal lobe consistent with silent infarcts. She has no allo- or autoantibodies, and is on an iron chelator, with a ferritin level under 1000 ng/mL. She wants to know when she can discontinue transfusion therapy.