Intravenous Gammaglobulin for Sickle Cell Pain Crises

Each subject must fulfill each of the following Inclusion/Exclusion criteria at screening and continue to fulfill these criteria prior to dosing: Inclusion Criteria: * Documented Sickle Cell Disease (SS or S-β thalassemia genotype) * Age 12-65 years for Phase 1 (Completed), 6-13.99 years for Phase 2 (Ongoing) * Normal stroke risk as assessed by transcranial Doppler (TCD). A normal TCD in subjects 16 years of age and younger within the year prior to study drug administration are required * Uncomplicated acute vaso-occlusive crisis requiring hospital admission and parenteral narcotic analgesics * If prescribed Voxelotor: Consistent daily use of voxelotor in the past week AND able to continue Voxelotor inpatient OR no reported use in prior week Exclusion Criteria: * Concomitant acute process, including acute chest syndrome, potential serious infection, or clinically significant bleeding * Fever \> 38.5° C and clinical suspicion of infection * Serum alanine aminotransferase \>4x Upper Limit of Normal (ULN) * Serum creatinine ≥1.3 mg/dL (or \> than 95th percentile for age) or \>300 mg/dL protein in spot urinalysis * Known condition associated with renal dysfunction including but not limited to diabetes mellitus, uncontrolled hypertension, multiple myeloma, and congestive heart failure * Any clinical evidence of prior stroke * Prior thromboses or current estrogen use * Current estrogen use * Hb \< 5 g/dL or \> 10 g/dL * Known Immunoglobulin A (IgA) deficiency or known allergy t…