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Bone and Spinal Muscular Atrophy
Silvia Vai1, Maria Luisa Bianchi1, Isabella Moroni2
1Experimental Laboratory for Children's Bone Metabolism Research, Bone Metabolism Unit, Institute Auxologico Italiano IRCCS, Milan, Italy.
Insights
Spinal Muscular Atrophy (SMA) patients show poor bone health, including low bone density and increased fractures. Early monitoring for osteopenia and osteoporosis is crucial for children with SMA.
Area of Science:
- Pediatric Endocrinology
- Neuromuscular Disorders
- Bone Metabolism
Background:
- Spinal Muscular Atrophy (SMA) is a genetic neuromuscular disease causing muscle atrophy.
- Bone health in pediatric SMA populations remains under-investigated.
- Understanding bone status is critical for comprehensive SMA patient care.
Purpose of the Study:
- To assess bone metabolism, bone mineral density (BMD), and fracture incidence in children with SMA types 2 and 3.
- To identify potential risk factors for bone derangements in this population.
- To evaluate the prevalence of asymptomatic fractures in young SMA patients.
Main Methods:
- Evaluated 30 children (15-171 months) with SMA types 2 and 3.
- Measured bone resorption markers (CTx) and 25-OH vitamin D levels.
- Assessed lumbar spine bone mineral apparent density (BMAD) Z-scores and analyzed fracture data from clinical records and spine X-rays.
Main Results:
- 60% of children had elevated CTx levels, indicating increased bone resorption.
- 50% of children had low lumbar spine BMAD Z-scores (<-1.5).
- 9 previously undiagnosed vertebral fractures were found in 7 children; 4 children had peripheral fractures.
Conclusions:
- Children with SMA exhibit reduced bone density, low vitamin D, and high bone turnover.
- Asymptomatic vertebral and peripheral fractures are prevalent, even in young SMA patients.
- SMA patients are at significant risk for osteopenia, osteoporosis, and fractures, necessitating early intervention.
Abstract:
Spinal Muscular Atrophy (SMA) is an autosomal recessive neuromuscular disease, leading to progressive denervation atrophy in the involved skeletal muscles. Bone status has been poorly studied. We assessed bone metabolism, bone mineral density (BMD) and fractures in 30 children (age range 15-171 months) affected by SMA types 2 and 3. Eighteen children (60%) had higher than normal levels of CTx (bone resorption marker); 25-OH vitamin D was in the lower range of normal (below 20 ng/ml in 9 children and below 12 ng/ml in 2). Lumbar spine BMAD (bone mineral apparent density) Z-score was below -1.5 in 50% of children. According to clinical records, four children had sustained four peripheral fractures; on spine X-rays, we observed 9 previously undiagnosed vertebral fractures in 7 children. There was a significant inverse regression between PTH and 25-OH D levels, and a significant regression between BMC and BMAD values and the scores of motor-functional tests. Even if this study could not establish the pathogenesis of bone derangements in SMA, its main findings - reduced bone density, low 25OH vitamin D levels, increased bone resorption markers and asymptomatic vertebral fractures also in very young patients - strongly suggest that even young subjects affected by SMA should be considered at risk of osteopenia and even osteoporosis and fractures.
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