Very, very cool: British doctors have combined gene therapy and bone marrow transplantation to cure 18 month-old Rhys Evans of SCID. (SCID is a disease wherein both forms of lymphocytes — the heavy lifters of the immune system — are defective as a result of a single genetic defect, causing the need to live in total, sterile isolation from the rest of the world due to an inability to fight infection.)

Diseases like SCID are perfect for this form of potential cure; the defect originates in cells produced by the bone marrow, and since doctors have been performing bone marrow transplants for decades, using gene therapy to correct the defect in a small population of cells and then replacing the defective marrow with the corrected cells is as close to a cure as you can get. In the coming months to years, we should be hearing about attempts to use the technique for other diseases that are similarly terrific candidates, the largest of which is sickle cell disease.