Patient description: The patient is a 34-year-old African American man with the known history of Sickle cell disease comes to the clinic with severe bone pain. The patient had severe pain in his lower back that radiated to both thighs scored 9 out of 10. The patient has had positive history of sickle cell crises since childhood. He also had the same symptoms in past two weeks treated with oxycodone which was not beneficial to his pain. His PCP sent him to the emergency department to receive intra venous pain modulators. The patient is afebrile within the normal blood pressure. No splenomegaly was detected in the physical exam. He has no positive history of drug allergy. He won't smoke or uses any illicit drugs. The lab study is as bellow: Hgb: 8 g/dl WBC: 10000 /mm3 Plt: 300000 /ml MCV: 106 fL Hemoglobine electrophoresis: 91% HbS 6%HbF 3%HbA2 AST: 22 U/L ALT: 43 U/L Alk P: 53 U/L Ferritin: 1200 ng/ml

Clinical trial eligibility criteria: eligible ages (years): 3.0-19.0,  Sickle Cell Disease SCD (genotype hemoglobin SS disease [Hb SS], genotype hemoglobin SC disease [HbSC],sickle ß°[Sß°] thalassemia, or sickle ß^+[Sß^+]thalassemia) with one or more of the following: 1. Patients must have symptomatic SCD (genotype Hb SS, Hb SC, Sß° thalassemia or Sß+ thalassemia), AND have 1 or more of the following clinical complications:(i) Clinically significant neurologic event (stroke) or any neurologic deficit lasting more than 24 hours that is accompanied by an infarct on cerebral MRI; OR (ii) patients who have a Transcranial Doppler (TCD) velocity that exceeds 200 cm/sec by the non-imaging technique (or TCD measurement greater than 185 cm/sec by the imaging technique) measured at a minimum of 2 separate occasions one month or more apart; OR, 2. Minimum of two episodes of acute chest syndrome in the 2 years before study entry, defined as new pulmonary alveolar consolidation involving at least one complete lung segment (associated with acute symptoms including fever, chest pain, tachypnea, wheezing, rales, or cough that is not attributed to asthma or bronchiolitis) despite adequate supportive care measures 3. History of 3 or more severe pain events per year in the 2 years before study entry Lansky/Karnofsky performance score greater than or equal to 40 Patients must have an unrelated adult bone marrow donor who is Human Leukocyte Antigen (HLA)-matched at 8 of 8 HLA-A, -B, -C and -DRB1 at high resolution using DNA-based typing Patients with adequate physical function: a)Cardiac: Left ventricular ejection fraction (LVEF) greater than 40%, or LV shortening fraction greater than 26%; b) Pulmonary: Pulse oxymetry with a baseline O2 saturation of greater than or equal to 85% is required for all patients, Carbon Monoxide Diffusing Capacity (DLCO) greater than 40% (corrected for hemoglobin) for patients in whom pulmonary function testing can be performed; c) Renal: Serum creatinine less than or equal to 1.5 x upper limit of normal for age and glomerular filtration rate (GFR) greater than 100 mL/min/1.73 m. For patients older than or equal to 16 years of age, GFR should be greater than 70 mL/min/1.73 m^2; d) Hepatic: Serum conjugated (direct) bilirubin less than 2x upper limit of normal for age as per local laboratory; alanine transaminase (ALT) and aspartate transaminase (AST) less than 5 times upper limit of normal as per local laboratory If the patient has been receiving chronic transfusion therapy for more than or equal to 1 year AND has clinical evidence of iron overload (serum ferritin level of greater than 1000 ng/ml), a liver biopsy shall be obtained within 90 days of starting conditioning therapy (alemtuzumab). Histologic exam of the liver must document absence of bridging fibrosis or cirrhosis of the liver. In other cases, a liver biopsy is optional Hemoglobin S (Hb S) level less than or equal to 45%, seven days prior to initiation of alemtuzumab  Evidence of uncontrolled bacterial, viral or fungal infections (currently taking medication and progression of clinical symptoms) within 1 month prior to starting the conditioning regimen. Patients with fever or suspected minor infection should await resolution of symptoms before starting the conditioning regimen Pregnant or breastfeeding Patients with 8/8 HLA-matched family donors able to donate Seropositivity for HIV Prior allogeneic marrow or stem cell transplant Iron chelation must be discontinued more than or equal to 48 hours before initiating the conditioning regimen Hydroxyurea (if receiving this therapy) must be discontinued more than or equal to 48 hours before initiating the conditioning regimen