Bone Abstracts

Objectives: To evaluate vitamin D and bone mineral density (BMD) status in children with Duchene muscular dystrophy (DMD) in relation to fractures and ambulation status using gross motor scale function classification system (GMFCS).

Methods: Clinical data of 53 DMD patients (mean age 12.1 years, range 4.9–19.6) at the first visit to the Endocrine/Bone Clinic at Nationwide Children’s Hospital were retrospectively studied. The patients were stratified to two groups according to GMFCS score of 1–3 (ambulatory) and 4–5 (non-ambulatory) and presence or absence of fractures.

Results: Vitamin D insufficiency was found in 72.7% (25OHD <30 ng/ml) or 25% (25OHD <20 ng/ml) of the patients. Overt vitamin D deficiency (25OHD <10 ng/ml) was observed in 2.2%. Thirty patients (56.6%) had fractures, 7 (23.3%) of whom had vertebral fractures. Patients with GMFCS score of 1–3 (n=27 or 50%, mean age 9.7±2.6 years) had higher mean lumbar and total body BMD height-adjusted z-score (HtZ) than those with GMFCS 4–5 (mean age 14.5±2.4 years) (lumbar HtZ −0.09±1.07 vs −1.042±1.5, P=0.03, total body HtZ −2.5±2.0 vs −5.6±2.5, P=0.0002), and also less fractures (0.6±0.8 vs 1.2±1.2, P=0.046). Mean duration of steroid treatment was longer in patients with fractures than those without fractures (5.9±3.2 vs 4.1±2.5 years, P=0.03), but was not significantly different between those with low or high GMFCS score. Height z-score was lower in those with fractures than those without (P=0.031). There were no correlations between 25OHD and fractures or 25OHD and BMD. There were no differences in mean 25OHD and BMD HtZ between those with and without fractures.

Conclusions: Non-ambulatory DMD patients had more fractures and worse BMD z-scores than those who were ambulatory, as expected. Factors associated with fractures were short stature, long duration of steroids, and the ambulation status, but not vitamin D and BMD z-score. Duration of steroid treatment did not correlate with ambulatory status, likely explained by early loss of ambulation following fractures of lower extremity in some patients, independent of duration of steroid use.

Disclosure: The authors declared no competing interests.