title: Cortical and trabecular bone density in X-linked hypophosphatemic rickets.
abstract: BACKGROUND
  X-linked hypophosphatemic rickets is caused by mutations in PHEX. Even though the disease is characterized by disordered skeletal mineralization, detailed bone densitometric studies are lacking.
  
  
  OBJECTIVE
  The aim of the study was to assess volumetric bone mineral density (vBMD) in X-linked hypophosphatemic rickets using forearm peripheral quantitative computed tomography.
  
  
  METHODS
  The study was conducted in the metabolic bone clinic of a pediatric orthopedic hospital.
  
  
  METHODS
  Thirty-four patients (age, 6 to 60 years; 24 female) with PHEX mutations were studied, of whom 7 children (age, 6 to 11 years) were actively being treated with calcitriol and phosphate supplementation. Twenty-one patients (age, 16 to 40 years) had received the same therapy before but had discontinued the treatment; 6 patients (age, 12 to 60 years) had never received this treatment.
  
  
  METHODS
  Trabecular and cortical vBMD of the radius.
  
  
  RESULTS
  Trabecular vBMD was elevated (mean age-specific and sex-specific z-score: +1.0) when all patients were analyzed together, due to very high results in currently treated patients (mean z-score: +2.4) and slightly above-average mean values in the other patients. Cortical vBMD was low when the entire cohort was analyzed together (mean z-score: -3.3), but was higher in currently treated patients (mean z-score: -1.3) than in patients who had discontinued therapy (mean z-score: -3.8) or who had never been treated (mean z-score: -4.1).
  
  
  CONCLUSIONS
  Patients with PHEX mutations have elevated trabecular vBMD at the distal radius while receiving calcitriol and phosphate supplementation, but low cortical vBMD at the radius diaphysis. Low cortical vBMD presumably reflects the underlying mineralization defect that is not entirely corrected by current treatment approaches.
authors.affiliation: Shriners Hospital for Children and Department of Pediatrics, McGill University, Montreal, Quebec, Canada H3G 1A6.
authors.forename: Moira
authors.initials: M
authors.lastname: Cheung
authors.forename: Paul
authors.initials: P
authors.lastname: Roschger
authors.forename: Klaus
authors.initials: K
authors.lastname: Klaushofer
authors.forename: Louis-Nicolas
authors.initials: LN
authors.lastname: Veilleux
authors.forename: Peter
authors.initials: P
authors.lastname: Roughley
authors.forename: Francis H
authors.initials: FH
authors.lastname: Glorieux
authors.forename: Frank
authors.initials: F
authors.lastname: Rauch
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000187:drug effects; D000328:Adult; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000627:therapeutic use; D001862:Bone Resorption / Q000209:etiology* / Q000517:prevention & control; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D002117:Calcitriol / Q000627:therapeutic use; D002648:Child; D002657:Child Development / Q000187:drug effects; D015331:Cohort Studies; D003131:Combined Modality Therapy; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D053098:Familial Hypophosphatemic Rickets / Q000235:genetics / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D040181:Genetic Diseases, X-Linked; D006776:Hospitals, Pediatric; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D053402:PHEX Phosphate Regulating Neutral Endopeptidase / Q000235:genetics / Q000378:metabolism; D010710:Phosphates / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D050071:Bone Density Conservation Agents; D010710:Phosphates; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; C506231:PHEX protein, human; D002117:Calcitriol