Task: Question Answering
Input (English): Context: Gene therapy is the insertion of genes into a persons cells to cure a genetic disorder. Could gene therapy be the cure for AIDS? No, AIDS is caused by a virus. Gene therapy only works to fix disorders caused by a faulty gene. The patient would have had this disorder from birth. Though gene therapy is still in experimental stages, the common use of this therapy may occur during your lifetime. There are two main types of gene therapy: 1. One done inside the body ( in vivo). 2. One done outside the body ( ex vivo). Both types of gene therapy use a vector, or carrier molecule for the gene. The vector helps incorporate the desired gene into the patients DNA. Usually this vector is modified viral DNA in which the viral genes have been removed. Dont worry, the virus used in gene therapy has been deactivated. During in vivo gene therapy, done inside the body, the vector with the gene of interest is introduced directly into the patient and taken up by the patients cells ( Figure 1.1). For example, cystic fibrosis gene therapy is targeted at the respiratory system, so a solution with the vector can be sprayed into the patients nose. Recently, in vivo gene therapy was also used to partially restore the vision of three young adults with a rare type of eye disease. In ex vivo gene therapy, done outside the body, cells are removed from the patient and the proper gene is inserted using a virus as a vector. The modified cells are placed back into the patient. One of the first uses of this type of gene therapy was in the treatment of a young girl with a rare genetic disease, adenosine deaminase deficiency, or ADA deficiency. People with this disorder are missing the ADA enzyme, which breaks down a toxin called deoxyadenosine. If the toxin is not broken down, it accumulates and destroys immune cells. As a result, individuals with ADA deficiency do not have a healthy immune system to fight off infections. In the gene therapy treatment for this disorder, bone marrow stem cells were taken from the girls body, and the missing gene was inserted into these cells outside the body. Then the modified cells were put back into her bloodstream. This treatment successfully restored the function of her immune system, but only with repeated treatments. 
 Question: which disorder has been treated by ex vivo gene therapy?
Output (English): ada deficiency