Ariane, if they have tested all of you and they haven’t come up with another mutation than it is indeed very unlikely that your son has NCCAH.  Though, it could still be that there is another mutation around but they haven’t tested for it (They usually test for the eight most common mutations and if they don’t detect what they are looking for they do more thorough testing which includes many more possibilities.  In your case, besides if your toddler also has rare defects and they had to do it anyway to realize what he has, they already found what they where looking for with the first set of testing and it wasn’t necessary.), or it could be that he has a mutation which wasn’t discovered yet (They come up with new ones all the time.). 

There are also some people who are symptomatic even they only carry one mutation. 

Another likelihood is that he has SVCAH.  My endo at Cornell told me that they have some families who have children with both SV and SW CAH with the same mutations.  Mostly I would guess, if it is so, you should have detected it already by age eight.  So it is also not a very big possibility.

It’s good that you are going for testing.  That way you’ll know for sure what’s going on.

Good luck

Risty