I think that a muscle biopsy is the only true way to determine whether your son has DMD or BMD. I was told by a geneticist that our son should have a biopsy done but other docs have said, no, it's DMD so don't. The geneticist had said something about our son's duplication was in the area of BMD. I wasn't successful in trying to contact the geneticist after many tries, but I understand that the 40's region of exons is in the more milder region.
The gene is huge and it has a beginning and an end - 1 though 79 exons and introns. The gene itself is not on a straight line - it folds and has hinges. If you have a mutation at the beginning or end or along the hinges, then it is more likely that you have a more severe mutation....When you have a biopsy done, the muscle is analyzed for dystrophin and if there is some dystrophin, even as little as 5% is helpful. Even BMD can be severe too....it's all on a continuim.
When a mutation is out of frame, I think it is more likely that the protein is trundicated - or terminated. Therefore, when a mutation is out of frame, then it is more likely that the disease is DMD vs. BMD. I recall that Leiden University has a genetic section that has a page where you can imput the mutation and it will tell you whether it's in or out of frame. I honestly don't know if it is that accurate though.
By the way, there are really three types of this type of MD, one that is DMD, one that is BMD and what is referred to as IMD - intermediate type. The differences are based upon the amt of dystrophin that is produced or not produced depending on the type of MD.
I think that your son has a deletion of 44 isn't that bad....and I know that exon skipping is working on 50 and 51 - skipping them. I would bet that 44 is possible. I have even read about someone that has a huge genetic mutation (14 deletions or more) and it is still BMD. I think there is so much to still learn about these disease...
Will's mom - age 6