My son is 17 and has had 2 DNA tests and they both have come back as "no mutation or deletion detected." One of the tests, done at the City of Hope was supposed to pick up 98% (I believe) of all possible deletions and mutations. We are looking into what other possible DNA tests there are so we can find out what his particular mutation or deletion is. My son was diagnosed 8 years ago at age 9, his neuro says they have made a lot of advances in the testing since then. There has to be some deletion or mutation or they wouldn't have MD, it is just a matter of finding it. I believe that there are some more common deletions and they are more easily detected. My sons initial diagnosis was from an exam and was confirmed by his muscle biopsy.
My son's deletion was detected, but one of my good friends (who is not on this board much) can't find her son's mutation either. I can't imagine the frustration! His DMD was diagnosed by biopsy as well. I can tell you that Utrophin is mutation independent, so it really does not matter what your mutation is like Exon Skipping or PTC124. This is not an answer to your questions, but I hope it helps your pain some!
We recently traveled to Clumbus Ohio, and are having more test done. I am not even sure what tests they are doing all I know is that it is going to take like four months. Hopefully they are doing gene sequencing??