Abstract
**Background:** Spinal muscular atrophy (SMA) is a disease affecting infants and young children, inherited in an autosomal recessive pattern with an incidence of approximately 1:10,000 live births, of which approximately 45-60% are Type I. According to the literature, 95% of SMA cases are caused by a homozygous deletion in the SMN1 gene on chromosome 5q13; the remaining 5% are associated with other mutations. The disease progresses with gradual motor deterioration, with severity depending on the disease type, and most patients ultimately develop motor disability and death. **Diagnosis:** Spinal muscular atrophy in children is diagnosed based on clinical presentation, typically manifesting as delayed motor milestones, arrest of motor development, and motor regression, combined with suggestive electromyography findings. Children undergo genetic testing to detect a homozygous deletion of the SMN1 gene; if not identified, further testing is performed to investigate other mutations causing neuromuscular disease. **Gene Replacement Therapy:** Since 2020, the Department of Neurology at Children's Hospital 2 has participated in a drug access program providing AVXS-101 (Onasemnogene Abeparvovec), also known as Zolgensma, for the treatment of spinal muscular atrophy in children under 2 years of age who have never experienced and are not currently experiencing respiratory failure at the time of treatment. This drug is a recombinant biologic product consisting of an AAV9 (Adeno-Associated Virus 9) capsid shell containing cDNA (complementary deoxyribonucleic acid) of the human SMN (Survival Motor Neuron) gene, which is non-replicating and non-integrating. During the two-year period from 2020 to 2022, 30 cases met the eligibility criteria for the drug access program. Eleven children were treated with Zolgensma at Children's Hospital 2, including 5 children infused in 2020, 5 children in 2021, and 1 child in 2022. All children tolerated the treatment well. The main adverse effects were elevated liver enzymes, followed by thrombocytopenia, both of which could be controlled with prednisone. All children showed some degree of improvement in motor function, most notably in the head/neck muscle groups and upper extremities. **Conclusion:** Spinal muscular atrophy in young children requires early screening and diagnosis to facilitate timely intervention and access to gene replacement therapy opportunities.
