title: The muscle-bone relationship in X-linked hypophosphatemic rickets.
abstract: BACKGROUND
  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.
  
  
  METHODS
  The study was carried out in the outpatients department of a pediatric orthopedic hospital.
  
  
  METHODS
  Thirty individuals with XLH (6 to 60 y; 9 male patients) and 30 age- and gender-matched controls participated.
  
  
  METHODS
  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.
authors.affiliation: Shriners Hospital for Children and Department of Pediatrics, McGill University, Montréal, Québec, Canada. lnveilleux@shriners.mcgill.ca
authors.forename: Louis-Nicolas
authors.initials: LN
authors.lastname: Veilleux
authors.forename: Moira S
authors.initials: MS
authors.lastname: Cheung
authors.forename: Francis H
authors.initials: FH
authors.lastname: Glorieux
authors.forename: Frank
authors.initials: F
authors.lastname: Rauch
mesh_terms: D000293:Adolescent; D000328:Adult; D015519:Bone Density; D001862:Bone Resorption / Q000000981:diagnostic imaging / Q000209:etiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D015331:Cohort Studies; D053098:Familial Hypophosphatemic Rickets / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D040181:Genetic Diseases, X-Linked; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D024510:Muscle Development; D018908:Muscle Weakness / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000209:etiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D010012:Osteogenesis; D011237:Predictive Value of Tests; D013977:Tibia; D014057:Tomography, X-Ray Computed; D055815:Young Adult