This study is for patients that have been diagnosed with multisystem Langerhans cell histiocytosis (LCH). The purpose of this study is to find out if prolonging the treatment and adding a drug called 6-mercaptopurine will be beneficial. Other goals include fining out if these changes will result in fewer patients having relapse of their LCH, and fewer patients having long term disease related problems. Participants can expect to be in this study for up to 24 months and will be followed on this study fir at least 5 years.

The purpose of the study is to generate a bio bank of specimens for research. We will tissue that would otherwise be discarded from clinical or surgical procedure and information from medical records. We will also collect discarded blood, urines and sputum. Collecting samples will help to better understanding the mechanisms of cardiovascular diseases, identify biomarkers for early diagnosis and to predict safety and efficacy of new therapies.

This study if for patients that have a blood disease and it's been determined that the best option for treating that blood disease is a cord blood transplant. Cord blood (CB) is blood that is taken from the umbilical cord and placenta of healthy newborn babies after childbirth. The cord blood collected from a newborn baby is called a cord blood unit. The United States Food and Drug Administration (FDA) considers cord blood to be a biological drug. These are considered "investigational" products. This study will evaluate the safety of administration of the investigational cord blood units by carefully documenting all infusion-related problems.

The primary purposes of this study are to:
•Provide access to cord blood units for recipients whose best choice for a cord blood unit(s) do not meet all FDA standards, but do meet standards set by the NMDP on this study.
•Assess how well and how quickly blood counts return to normal after transplant in recipients on this study.

The Center for International Blood and Marrow Transplant Research (CIBMTR ) keeps a research database. It uses this database to collect and study the medical data for patients that have received Hematopoietic Cell Transplantation, Other Cellular Therapies and Marrow Toxic Injuries. It also collects and studies data from donors who give bone marrow or peripheral blood stem cells (PBSCs). These therapies are used to treat cancer and other diseases. The purpose of this study is to add more data to the database. Participants will have medical data (data about their disease, transplant or cellular therapy) collected before and after transplant cellular therapy, and once a year afterwards for life.

The primary purpose of the Research Sample Repository is to make blood samples available for research studies related to histocompatibility and hematopoietic cell transplantation (HCT) or other cellular therapy.