US clinicians report the observation of two unrelated patients with SMN1-related proximal spinal muscular atrophy who developed signs of necrotising enterocolitis (NEC) within days of intravenous administration of the gene therapy product Zolgensma® (onasemnogene abeparvovec).
- The two infants had been diagnosed at birth as part of the screening programme in place in the USA.
- They were treated very rapidly (18 days of life for one, 21 days for the other).
- Both had two copies of the SMN2 gene and one was clearly symptomatic at the time of injection.
- The NEC episode resolved and the children are currently doing well.
The pathophysiology of this rare complication remains unclear, but the gene therapy is probably to blame. The other explanation could be linked to the fact that these children were probably cases of SMA type 0 (the earliest and most severe form of SMA).
