American clinicians involved in gene therapy designed to deliver a truncated version of the dystrophin gene (microdystrophin) by vein, using an adeno-associated virus, have reported a complication that was already known but rarely encountered:
- the patient was 9 years old and still able to walk at the time of gene therapy (GT),
- his genotype corresponded to a large deletion (exons 3 to 43),
- he was taking part in the phase 3 ENDEAVOR trial promoted by the Sarepta laboratory,
- one month after injection, a limb-girdle muscle deficit and bulbar problems appeared,
- serum CPK levels rose to 28,000 IU/l and histology was clearly in favour of myositis,
- prolonged immunosuppressive treatment enabled the patient to return to a pre-TG state.
This is the first published case for which exhaustive data are available (of the six reported by the various laboratories). The predominance of bulbar disorders as the mode of presentation is also noteworthy.
