Osteoarthritis, Osteophytes and Enthesophytes Affect Biomechanical Function in Adults with X-linked Hypophosphatemia

CONTEXT: X-Linked hypophosphatemia (XLH) is a lifelong metabolic disease with musculoskeletal comorbidities that dominate the adult clinical presentation. OBJECTIVE: The adult XLH disorder has yet to be quantified on the basis of the physical and functional limitations that can affect activities of daily living. Our goal was to report the impact of the musculoskeletal manifestations on physical function. DESIGN AND SETTING: Musculoskeletal function was evaluated by validated questionnaires and in an interdisciplinary clinical space where participants underwent full-body radiologic imaging, goniometric range of motion (ROM) measurements, general performance tests, and kinematic gait analysis. PATIENTS: Nine adults younger than 60 years with a diagnosis of XLH and self-reported musculoskeletal disability, but able to independently ambulate, were selected to participate. Passive ROM and gait analysis were also performed on age-approximated controls to account for differences between individual laboratory instrumentation. RESULTS: Enthesophytes, degenerative arthritis, and osteophytes were found to be consistently bilateral and diffusely present at the spine and synovial joints across participants, with predominance at weight-bearing joints. Passive ROM in adults with XLH was decreased at the cervical spine, hip, knee, and ankle compared to controls. Gait analysis relative to controls revealed increased step width, markedly increased lateral trunk sway, and physical restriction at the hip, knees, and ankle joints that translated into limitations through the gait cycle. CONCLUSIONS: The functional impact of XLH musculoskeletal comorbidities supports the necessity for creating an interprofessional health-care team with the goal of establishing a longitudinal plan of care that considers the manifestations of XLH across the lifespan.