Many primary immunodeficiencies are lethal diseases. In the absence of treatment SCID cause death within the first year of life. Allogenic hematopoietic stem cell transplantation (HSCT) can cure these diseases. However, HSCT is associated with several serious adverse events such as toxicity of myeloblative chemotherapy and the consequences of the potential immune conflict between donor and recipient.

In the case of ADA-SCID there were two ways of treatment. The first was regular injections with the ADA enzyme; the second was a bone marrow transplant from a compatible donor. If neither of these treatments was possible, the only way affected children could survive was by total isolation in an artificial, germ-free environment. For this reason, children suffering from SCID are often known as ‘bubble babies’.