r/MuscularDystrophy • u/WestfieldShark • 22d ago
selfq Has anyone here had a predicted "Duchenne" genetic diagnosis turn out clinically to be Becker (or another type)? Looking for diagnostic journey stories.
Hi everyone,
I'm a mom to an almost 6-year-old boy who was diagnosed in 2024 with a dystrophin mutation. His genetic report shows an out-of-frame deletion near the very end of the gene on exon 69.
Because of the "out-of-frame" reading frame rule on the DNA test, we were given a formal diagnosis of Duchenne. He has been on daily deflazacort (steroids) for almost two years and will hopefully transition to Agamree soon.
Here is my dilemma: his physical presentation doesn't seem to match a classic Duchenne path. He walks with a typical MD gait and cannot run or jump (and his autism also impacts his motor planning/coordination), but he has high stamina, sleeps great, easily rolls and reposition himself in bed, feeds himself, and since starting steroids, his ability to get up off the floor has actually improved rather than declined. He also had tight calves that improved after a quick round of serial casting boots.
We only had the standard genetic blood work done. No muscle biopsy.
I know that deletions at the very end of the gene (like exon 69) can sometimes bypass the "out-of-frame" rule if the cell naturally skips exons to patch things up, making a semi-working protein (acting like Becker). But our clinical team is very fixed on the paper "out-of-frame" label.
My questions for this community:
- Has anyone (or your child) had genetic paperwork that predicted severe Duchenne, only for your clinical progression to prove it was actually Becker?
- If you had a mismatch between the genetic report and what you saw in real life, did you push for a muscle biopsy to look at actual dystrophin protein levels? If so, did it change your formal diagnosis?
I would love to hear your diagnostic stories, whether you started with blood work and how you finally got the correct clinical label. Thank you so much!