In 1990, the first clinical gene therapy was administered to a four-year-old girl to treat a specific genetic disorder. Identify the disorder from the given options.

Step-by-step solution

The first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. Answer: Adenosine deaminase (ADA) deficiency