183PThe impact of genotype on north star ambulatory assessment in individuals with Duchenne muscular dystrophy treated with corticosteroids: a single-center study of 416 patients

Abstract

Previous studies have shown that certain genotypes in Duchenne muscular dystrophy (DMD) result in variable disease severity. Some of these studies included individuals treated and not treated with corticosteroids while others included multiple sites with varying care standards. This study aims to assess motor function in ambulatory DMD, as measured by the North Star Ambulatory Assessment (NSAA), and its correlation to genotypes in a large cohort of individuals with DMD treated with corticosteroids at a single center. This retrospective review included medical records of individuals with DMD who were treated with corticosteroids for at least 12 consecutive months. Encounters were excluded if individuals were receiving disease-modifying therapy or in clinical trials. Data were analyzed using a linear model with repeated measures. 2098 encounters from 416 individuals were included. NSAA scores for the entire cohort improved in early childhood until plateauing around age 6 to 8.5 years, followed by a progressive decline at age 9 years. Four exon-skippable groups were compared at ages 7, 10, and 14 years to the rest of the cohort. For exon 51 skip-amenable group, NSAA scores at age 7 years were 2.46 points lower (p=.009) but declined less rapidly than the rest of the cohort. For exon 53 skip-amenable group, NSAA scores at age 7 years were 2.54 points lower (p=.029) and declined at a similar rate compared to the rest of the cohort. For exon 44 and 45 skip-amenable groups, there was no significant difference in NSAA scores at these ages compared to the rest of the cohort. These findings are in line with previous observations of genotype-phenotype correlations in DMD and provide enhanced information for trial design and clinical management.