Supplementary Material for: Eculizumab for Thrombotic Microangiopathy Induced by Onasemnogene Abeparvovec in Spinal Muscular Atrophy

Introduction
Onasemnogene abeparvovec is one of the three disease-modifying therapies available that can significantly improve the outcome of patients with 5q-spinal muscular atrophy. Therapy-induced thrombotic microangiopathy is an ultra-rare, but potentially life-threatening condition of not yet clearly defined aetiology.
Case Presentation
A case of a 2-year-old patient with 5q-spinal muscular atrophy, who developed thrombotic microangiopathy after gene replacement therapy with onasemnogene abeparvovec is described. This severe adverse event was promptly recognised and successfully treated with the complement C5 inhibitor.
Conclusion
Thrombotic microangiopathy is an ultra-rare, but potentially life-threatening condition that can occur after onasemnogene abeparvovec therapy. Anticipation of these serious adverse event, its prompt recognition and treatment are crucial for a better outcome.