Bone Abstracts

We analyzed body composition (DXA, Hologic) in 334 young patients (aged 3–24 years) with chronic diseases, most of them on long-term glucocorticoid (GC) treatment, and monitored its changes over 3–14 years (6.9±6.2 years).

Bone mineral content (BMC), fat mass (FM) and fat-free mass (FFM) were measured on total body (TB), trunk, upper limbs, lower limbs. BMC, FM, FFM were expressed as percentages and compared with age- and sex-matched healthy Italian controls. BMI was also measured.

In 159 patients with nephrotic syndrome, connective tissue diseases, asthma, autoimmune hepatitis, or transplants (aged 3–20 years), GCs had major effects on trunk BMC and FM, related to cumulative dose. Independently of disease and age, BMC decrease and FM increase were higher during the first year of treatment (P<0.01 vs baseline), and continued more slowly thereafter.

In 39 walking boys with Duchenne muscular dystrophy (aged 4–15 years), BMC was low for age, and more reduced at lower than upper limbs. At lower limbs, FM progressively increased and FFM decreased over time. The FFM decrease correlated with changes in muscle strength (evaluated by Manual Muscle Testing, MRC scale), P<0.03.

In 136 patients affected by cystic fibrosis (aged 3–24 years; 64 F), body composition analysis showed decreased FFM and FM with respect to controls in both sexes, for both TB and the three sub-regions. We observed significant correlations of BMI with FFM (P<0.01); FFM with both TB BMC and lower-limbs BMC (P<0.02); FFM, FM, and BMI with trunk BMC (FFM showing the highest correlation); FFM with FEV1, a pulmonary function index (P<0.02).

In children and young patients, body composition analysis is a powerful tool to evaluate the disease-related deviations from normal; to demonstrate the GC influence on BMC, FM, and FFM; to highlight the relationship between muscular strength/activity and bone.