In humans, XSCID affects one in 100,000 boys, resulting from the inheritance of a faulty gene on one of the mother's X-chromosomes. It often proves fatal before the child's first birthday. The disease first came to public attention in the late 1970s with the "Bubble Boy," David Vetter, who lived his entire life in a sterilized environment in order to protect him from outside germs. Vetter died in 1984.
The only treatment for XSCID is through a bone-marrow transplant from a normal donor designed to replenish the hematopoietic stem cells that are capable of constantly renewing new functional immune cells, or, more recently, gene therapy that works by replacing the defective gene with a normal gene in the patient's own cells. Gene therapy has been put to curative use against this disease in humans resulting in successful immune reconstitution in 10 of 11 boys in a 1999 French study. This clinical trial consisted of the standard ex-vivo approach to gene therapy in which bone-marrow cells were taken out of the body of the affected boy, cultured in vitro for five days with exposure to a retroviral vector containing the normal gene and transplanted back into the patient. Three of the boys unfortunately developed a T-cell leukemia attributed to the gene therapy resulting in the cessation of this study.