P.084 5q spinal muscular atrophy Canadian Paediatric Surveillance Program – 2020-2021 results

Abstract

Background: Spinal muscular atrophy (SMA) is the leading genetic cause of infant death and the second most common autosomal recessive disorder; most cases are due to homozygous deletion of SMN1 gene. Methods: This study uses the Canadian Paediatric Surveillance Program to determine the minimum annual incidence of 5q-SMA from birth to 18 years of age in Canada. The protocol can be accessed at www.cpsp.cps.ca/surveillance. Results: Eighteen cases were reported in 2020-2021. Ten (55%) cases were reported from Ontario and the remaining cases were reported from Atlantic Canada and Western Canada. Their median age was 11 months (IQR 4–21); 61% were male. The most common presenting symptoms were hypotonia and delayed motor milestones in 12 (86%) and 10 (71%) cases respectively. On average, the diagnosis was delayed after onset of symptoms by three months for SMA Type 1, by eight months for Type 2, and by 18 months for Type 3. Twelve (86%) cases received nusinersen as their first disease-modifying treatment. Conclusions: Early recognition and newborn screening are essential to reduce diagnostic delay and enable timely treatment of SMA. Other data sources including the Canadian Neuromuscular Disease Registry and molecular genetic laboratories will be used to estimate the annual incidence of pediatric SMA in Canada.