The Muscle-Bone Relationship in X-Linked Hypophosphatemic Rickets

Shriners Hospital for Children and Department of Pediatrics, McGill University, Montréal, Québec, Canada.
The Journal of Clinical Endocrinology and Metabolism (Impact Factor: 6.21). 03/2013; 98(5). DOI: 10.1210/jc.2012-4146
Source: PubMed


Context:We recently found that patients with X-linked hypophosphatemic rickets (XLH) have a muscle function deficit in the lower extremities. As muscle force and bone mass are usually closely related, we hypothesized that patients with XLH could also have a bone mass deficit in the lower extremities.Objective:The study objective was to assess the muscle-bone relationship in the lower extremities of patients with XLH.Setting:The study was carried out in the outpatients department of a pediatric orthopedic hospital.Patients and Other Participants:Thirty individuals with XLH (6 to 60 y; 9 male patients) and 30 age- and gender-matched controls participated.Main Outcome Measures:Calf muscle size and density as well as tibia bone mass and geometry were assessed by peripheral quantitative computed tomography. Muscle function was evaluated as peak force in the multiple 2-legged hopping test.Results:Muscle force was significantly lower in XLH patients than in controls but muscle cross-sectional area did not differ (after adjustment for tibia length). External bone size, expressed as total bone cross-sectional area, was higher in the XLH group than in controls. The XLH cohort also had statistically significantly higher bone mineral content.Conclusions:Patients with XLH have increased bone mass and size at the distal tibia despite muscle function deficits.