1. Study the influence of age, steroid use and ambulatory status on Vitamin D (vitD) levels in DMD boys. 2. Implementation of Bone Health Protocol (BHP) and its outcomes.

DMD is an inherited neuromuscular condition that increases risk for bone health problems, including vitD deficiency. Limited data exists on how different variables affect this risk.

Retrospective prospective study of DMD boys followed in the MDA clinic in a tertiary care Children’s Hospital from 2012-2019. Electronic medical records (EMR) for age, genotype, steroid use, ambulatory status and 25-HydroxyVitaminD (25OHD) levels reviewed and boys with two or more 25OHD levels recorded were included. In 2018, the BHP, an algorithm to diagnose and treat vitD deficiency, was implemented. Pre-and post-BHP vitD status was documented. Linear mixed effects models were used to assess vitD trajectories in different groups.

Hundred and fourteen DMD boys, average age 15.1 years (range 4-25 years), 69.3% (n=79) deletion/duplications, 24.5% (n=28) point mutations, 6.1% (n=7) unrecorded genetics were included. 65% (n=74) received steroids, 63% (n=72) were non-ambulatory. Three hundred and two 25OHD values were available with an average of 26.12 ng/ml (range <13-83 ng/ml). Sub-group analysis showed statistically significant difference (p<0.05) with higher vitD levels in ambulatory boys age <12 years, with no difference in steroid versus steroid naive group. Prospectively, 52 subjects with vitD deficiency enrolled in BHP with 15 subjects completing 6 months follow-up, showing statistically significant improvement in 25OHD levels.

25OHD levels are uniformly low in DMD boys. Linear mixed models showed a trend towards declining 25OHD levels with loss of ambulation and increasing age (>12 years), likely from multiple factors including poor compliance for vitD supplements and disease chronicity. Preliminary results from BHP implementation is showing promising improvement in 25OHD levels likely secondary to improved surveillance of vitD deficiency and uniform vitD deficiency treatment and supplementation.