Bone health in neuromyelitis optica: Bone mineral density and fractures.

Background: The bone health in neuromyelitis optica spectrum disorder with aquaporin-4 immunoglobulin G antibodies (NMOSD-AQP4) have not been fully evaluated. To evaluate the prevalence of fractures and bone loss in patients with NMOSD-AQP4 compared to healthy controls and patients with multiple sclerosis (MS) and to identify the risk factors associated with fractures and low bone mineral density (BMD) in patients with NMOSD-AQP4.

Methods: Seventy-one patients with NMOSD-AQP4 were included. The two control groups consisted of 213 age-, sex-, menopause-, and body mass index (BMI)-matched healthy participants from the Korean National Health and Nutrition Examination Survey (healthy controls) and 41 patients with multiple sclerosis (disease controls). We collected demographic and clinical data related to bone health including BMD and FRAX score.

Results: Patients with NMOSD-AQP4 had a higher prevalence of fractures than the healthy control group (OR = 5.40, CI = 2.004-14.524, p = 0.001), with falling, but not steroid use, being associated with an increased risk of fractures after diagnosis with NMOSD-AQP4 (OR = 24.902, CI = 3.086-200.947, p = 0.003). They also had significantly lower BMD than controls (femur neck, p = 0.044; total hip, p < 0.001), which was more prominent in young participants. The BMD in the NMOSD-AQP4 group was associated with cumulative dose of oral steroids, age, sex, BMI, and partly with the prophylactic calcium supplements. Though the patients with NMOSD-AQP4 did not differ significantly from patients with MS in terms of fracture rate and BMD, they had higher risk of fractures as measured by the Fracture Risk Assessment Tool (for major osteoporotic fractures, (p = 0.001; for hip fractures, p = 0.018).

Conclusion: Patients with NMOSD-AQP4 had a significantly higher risk of fractures that could mostly be attributed to falling. Additionally, low BMD was observed in these patients; it was more prominent among young patients, associated with steroid use, and may partially prevented by the use of prophylactic calcium supplements.