Bone Abstracts

Objectives: Poor bone health in boys with Duchenne Muscular Dystrophy (DMD) due to muscle weakness and glucocorticoid treatment is a major concern. This study assesses the bone health status in DMD boys with glucocorticoid treatment in a single centre.

Methods: A retrospective chart review from January 2009 to January 2017 was undertaken on all DMD cases with active follow-up in a single paediatric unit in a University-affiliated hospital. We assessed their vitamin D (25, OH) levels, areal bone mineral density (BMD) with DXA total body less head (TBLH) and lumbar spine (LS), and fracture frequency.

Results: Fifteen DMD boys were included (mean age 7.0 years, range: 3.9–12.9 years). Before glucocorticoid initiation, thirteen were at their good ambulatory state, one was at late ambulatory and one was at non-ambulatory state. None reported any fracture. All had BMD assessment with DXA. Mean Z-scores of LS (n=11) and TBLH (n=6) were −1.2±0.8 and −2.1±1.8 SD respectively. Six (40%) had low BMD for age (Z-score ≤−2.0 SD) and it was not associated with age (P=0.71) or vitamin D level (P=0.62). The mean vitamin D (25, OH) levels level was 38.7±12.1 nmol/L. Twelve (80%) had vitamin D insufficiency (<50 nmol/L). All were started on prednisolone at 0.5±0.1 mg/kg/day. At a mean follow-up of 2.9±1.4 years, eleven were still at their good ambulatory state, one was at late ambulatory and three were at non-ambulatory state. None reported any long bone fracture but one developed grade 3 vertebral fractures. DXA was repeated in nine and seven had low BMD for age. Two showed improved BMD Z-score at LS despite steroid treatment.

Conclusions: Vitamin D insufficiency and low BMD are common among DMD boys even before initiation of glucocorticoids. The use of long-term steroid further compromises their bone health status. The low baseline BMD noted at very young age and the difference observed in LS and TBLH Z-scores raised concern of the interpretation complexity of the DXA findings. A better bone imaging measure is needed for this group of children.

Disclosure: The authors declared no competing interests.