186PPerformance of upper limb in steroid-treated Duchenne muscular dystrophy: genotype-phenotype correlations

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease caused by absence or near absence of functional dystrophin protein that results in progressive weakness. Performance of Upper Limb (PUL) is a scale designed to measure upper limb motor performance changes of individuals with DMD. The latest iteration of PUL is 2.0, which has been used since 2015. Prior studies have demonstrated that the PUL scores of individuals with DMD begin to deviate from typically developing children at age 8 years. Differences have been reported between certain exon-skip amenable genotypes on the decline in PUL scores. The goal of this study was to assess the longitudinal changes in upper extremity motor function using PUL 2.0 scores of individuals with DMD treated with long-term glucocorticoid steroids and standard care at a single tertiary care center. Individuals were excluded if they were exposed to other disease modifying therapies. We retrospectively studied 188 patients with DMD with 972 PUL entry encounters that occurred from 4/12/2016 to 12/7/2023. The genotype distribution of our cohort was comparable to previously reported study cohorts. Mean steroid duration was 12.3 years. A mean total PUL score of 29.1 at ages <15 years, 23.5 between ages 15-20 years, and 18.2 at ages >20 years were demonstrated. The average PUL score decline of the entire group was 1.3 points per year. Secondary analysis was performed to evaluate the impact of genotype on PUL scores. Differences in PUL between certain exon skip-amenable genotypes were detected in the group above age 20 years with the exon 44 skip-amenable having higher scores and exon 51 skip-amenable having lower scores. Linear models demonstrated similar rates of decline by exon skip group but with a higher entry score for the exon 44 skip-amenable group, and lower for the exon 51 skip-amenable group. These data provide a reference dataset for PUL scores of steroid treated DMD patients.