There was a question about SMA in the live forum today and I wanted to provide some additional information:
From what I understand, the gene therapy has been effective for most infants. You are correct, though, that not all infants actually have access to the gene therapy. Insurance could be an issue. Also, families have to have access to an infusion center (be able to travel to a center). The research does show conclusively, though, that outcomes are best when the gene therapy infusions are started as close to birth as possible. Many states are now adding SMA to the newborn screen.
As of December, all states have added SMA to their NBS programs. Timing is everything in terms of disease modifying therapy and best outcomes; the sooner the treatment is administered, the better the outcomes. All three therapies have shown to be effective at modifying natural history trajectory.