100 Adults with Spinal Muscular Atrophy at the Dawn of Treatment: A Bone Health Focus

Introduction As disease-modifying treatments for spinal muscular atrophy (SMA) are implemented, co-morbidities in adults including osteo-pathologies are increasingly recognised. Guidance for managing such issues is incomplete. We present data on bone health from, to our knowledge, the UK’s largest single-centre adult SMA cohort. Objectives We aimed to quantify the following in our cohort: Fracture incidence and location Implementation of bone density scanning Vitamin D status and supplementation Methods Retrospective case note review was performed for 100 adult patients (51% male; 49% female, average age 32), at the National Hospital for Neurology and Neurosurgery from 2022-2025. SMA subtypes were SMA3 (N=55), SMA2 (N=44) and SMA1 (N=1). Where available ethnicities were: White (N=57), Asian (N=13), Black (N=4), Mixed (N=2) and Other (N=4). Results Fracture incidence was 25% (N=25), of which 85% (N=29) affected the lower limb(s). Most fractures (80%) (N=20) occurred in SMA3 patients. 50% (N=10) of SMA3 patients with a history of fractures, subsequently lost the ability to walk. Bone density scans were recorded in 40% (N=10) of patients who had fractures (90% of scans occurred post fracture), and in 17% (N=13) of non-fracture patients. Of the overall cohort, 39% (N=39) were vitamin D deficient or insufficient, and 60% (N=60) were prescribed cholecalciferol. Conclusions The high fracture rate is particularly pertinent, given that lower limb fractures can accelerate ambulation loss in SMA3 patients. Consistency in bone-density scanning is lacking and generally reactive to fracture occurrence. This highlights the importance of bone health considerations in adult SMA patients.