The correct answer is D: While gene therapy has potentially harmful results for some SCID patients, it has shown promising results in treating most SCID patients.
Option D is correct because the passage emphasizes gene therapy as a treatment for SCID, noting that 88% of children who received it had their immune systems restored.
It also mentions that some children treated for the X-linked form of the disease “have developed leukemia, and one has died,” while none of the children with ADA-SCID developed leukemia.
The passage concludes with medical researchers stating that gene therapy “is still a better alternative than most conventional treatments for X-linked SCID.”
Option A is incorrect because, although the passage mentions that a quarter of X-linked SCID patients developed leukemia, it emphasizes that gene therapy’s success “surpasses” other treatments and is “a better alternative than most conventional treatments.”
Therefore, the passage does not suggest that parents should hesitate or decide whether to choose gene therapy. The first half of this option regarding ADA-SCID is accurate, but the second half includes misleading information, so this choice can be eliminated.
Option B is incorrect because, while it is true that some X-linked SCID patients developed leukemia, the passage does not focus on gene therapy as inherently problematic.
Instead, it highlights that, despite potential risks, gene therapy is still a better alternative to conventional treatments. The main point is broader than the treatment being dangerous, so this option can be eliminated.
Option C is incorrect because it claims that gene therapy is the best method for treating SCID. The passage clarifies that the best treatment for this rare disease is a bone marrow transplant from a matched sibling.
Gene therapy is described as “a better alternative than most conventional treatments” and superior to unmatched donor transplants, but this does not support the claim that it is the best overall treatment.