Subcutaneous Ig in Allogeneic Stem Cell Transplant Recipients

Inclusion Criteria: * Age over 18 years * Patients at least 100 days post allogeneic hematopoietic cell transplantation for any benign or malignant hematological disease, from a related or unrelated donor * Patients who are already established on regular IVIG * Patients eligible for immunoglobulin replacement with an IgG \<7mg/L, or normal IgG total but IgG2 or IgG4 below normal * Patients with IgG =\>7g/L but with at least 2 prior episodes of bacterial infection (proven or suspected eg. sinusitis diagnosed on CT) * No other medical condition which would preclude treatment with immunoglobulin * Willing to participate and sign informed consent Exclusion Criteria: * Previous serious adverse reaction from IVIG or products from Hizentra (polysorbate) * Other serious medical or psychiatric disorders which may interfere with the patient's ability to participate in the study, or interfere with study assessment (e.g. advanced congestive heart failure, severe liver disease, renal failure, disease relapse or secondary malignancy, schizophrenia, paranoid psychosis)