Bone Health Determinants in Spinal Muscular Atrophy

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 224-247-Osteoporosis I
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-246
Natascia Di Iorgi*1, Giorgia Brigati2, Irene Olivieri3, Marta Ferretti3, Claudio Bruno3 and Mohamad Maghnie4
1University of Genova, IRCCS G Gaslini, Genova, Italy, 2IRCCS G Gaslini, Genoa, Italy, 3IRCCS G Gaslini, 4Univ of Genova/IRCCS Giannina, Genova, Italy
Purpose. Severe osteopenia and fractures are reported in spinal muscular atrophy (SMA). Aim of our study was to evaluate determinants of bone status in SMA patients.

Methods. DXA measurements of total body less head bone mineral density (TB-BMD,g/cm2 and Z-score), bone mineral content (TB-BMC, g), fat mass (FM%, kg) and fat free mass (FFM kg) were obtained at baseline (11,6±7,0 yrs of age) and at 2 further time points over a 36 months period in 17 SMA subjects (n=10 SMAII, 5 females, 5 males; n=7  SMAIII, 5 females, 2 male; n=14 below 20 yrs of age) and 21 controls (11 females and 10 males). All patients underwent height (HT SDS), body mass index (BMI SDS), FMI (FM, kg/m2) measurements. Five patients (n=3 males with SMAII, and 1 female and 1 male with SMAIII) reported fragility fractures.

Results. SMAII and SMAIII subjects did not differ at baseline for age, HT SDS, BMI, FM, FFM and FMI although SMAII tended to be shorter and more muscularly atrophic than SMAIII subjects at all time points. Control subjects were significantly taller compared to both SMA groups.

TB-BMC and BMD-Z-score values were significantly reduced in SMAII (331.3±153.6g and -2.4±1.0Z-score, respectively) compared to SMAIII (1016.2±864.1g and -1.5±0.8 Z-score, respectively) and controls (917.9±607.0g and -0.3±0.7 Z-score, respectively) at baseline and during follow up, while bone mass parameters did not differ significantly between control subjects and SMAIII patients. Controls showed a significantly different annualized increase of BMD (0,033±0.015g/cm2) compared to SMAII (0,018±0.015/cm2, P=0,04) and SMAIII (0,015±0.022m2, P=0.04), with an annualized TB-BMC increase of 113g compared to SMAII (32.2g, P=0.01) and SMAIII (39.7g, P=0.06). TB-BMD Z-score was inversely related to age in SMAII and fell below normal values for age and sex (<-2 Z-score) in 70% of SMAII subjects by the age of 15 yrs; only 1 SMAIII showed low bone mass.

DXA parameters did not discriminate between fractured and not fractured SMA patients. In contrast BMI, FM and FMI were significantly higher and FFM significantly reduced in SMAII subjects with fractures compared to SMAII without bone events (Ps<0,05).

Conclusions. SMAII patients present a profoundly compromised bone status, although  bone mass accrual is reduced also in SMAIII subjects compared to controls. Body composition may be a major determinant of skeletal fragility in SMAII patients.

Nothing to Disclose: ND, GB, IO, MF, CB, MM

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