Depends on the disease. Disclaimer, I'm not a doctor or researcher! YMMV Those diseases with active bad genes controlling the behavior of cells that are replac

Depends on the disease. Disclaimer, I'm not a doctor or researcher! YMMV Those diseases with active bad genes controlling the behavior of cells that are replaced at a fast rate would be more likely to effectively disappear after just the treatment, such as some blood or skin diseases. Those who changes how the body grows (like say skeleton growth or other cells with slow replacement) would still leave the body in the condition it was in just before the treatment. They would effectively be chronic unless you can simultaneously fix the existing faults using for example surgery or a secondary therapy. But they wouldn't continue to deteriorate in the cases where the continued activity of the bad gene drives the deterioration. And syndromes caused by genes that only had to be active once (like in childhood) and now is dormant won't get fixed by gene therapy (but it MIGHT prevent it from being hereditary, if properly propagated in the body)