An unexpected side effect of SMA gene therapy

Side effects of the onasemnogene abeparvovec (OA), the gold standard for gene therapy of infants with SMA, are rare but potentially worrying. Italian clinicians report the case of a child diagnosed at three weeks of age, treated first with nusinersen and then with OA at 5.5 months of age.

  • The patient presented a febrile episode with vomiting and loss of appetite shortly after the injection of OA.
  • The CPK level rose from 369 international units per litre to a transient peak of 1,755 IU/l on the fourth day, with the child’s condition improving in the meantime.
  • The authors describe this episode as myositis, although some signs were also suggestive of a minimal thrombotic microangiopathy.


Acute Benign Myositis Following Onasemnogene Abeparvovec Therapy in Type 1 Spinal Muscular Atrophy. Dosi C, Tozzo A, Masson R. Pediatr Neurol. 2022 Jun;131:23-24.