title: A two-year prospective controlled study of bone mass and bone turnover in children with early juvenile idiopathic arthritis.
abstract: OBJECTIVE
  To explore early changes and predictors of bone mass in children with juvenile idiopathic arthritis (JIA) in order to identify patients who will develop bone mass reductions.
  
  
  METHODS
  We conducted a prospective cohort study of 108 children with early JIA (ages 6-18 years; mean disease duration 19.3 months) who were individually matched with 108 healthy children for age, sex, race, and county of residence. Bone mass and changes in total body, spine, femur, and forearm bone mineral density and bone mineral content (BMC), body composition, growth, and biochemical parameters of bone turnover were examined at baseline and at followup a mean of 24 months later. Low bone mass was defined as a Z score >1 SD below the reference population.
  
  
  RESULTS
  Of the 200 children evaluated at followup, the 100 healthy children had greater gains in total body BMC (P = 0.035), distal radius BMC (P < 0.001), and total body lean mass (P < 0.001) than did the 100 JIA patients. Low or very low total body BMC was observed in 24% of the patients and 12% of the healthy children. Bone formation, bone resorption, and weight-bearing activities were reduced in the patients compared with the healthy children. Multiple regression analysis showed that in patients with JIA, serum bone-specific alkaline phosphatase, serum C-telopeptide of type I collagen, and weight-bearing activities were independent predictors of changes in total body BMC. Total body BMC was lower in patients with polyarticular onset than in those with oligoarticular disease onset.
  
  
  CONCLUSIONS
  Patients with JIA have moderate reductions in bone mass gains, bone turnover, and total body lean mass early in the disease course.
authors.affiliation: Rikshospitalet University Hospital, Oslo, Norway. gunhild.lien@chello.no <gunhild.lien@chello.no>
authors.forename: Gunhild
authors.initials: G
authors.lastname: Lien
authors.forename: Anne M
authors.initials: AM
authors.lastname: Selvaag
authors.forename: Berit
authors.initials: B
authors.lastname: Flatø
authors.forename: Margaretha
authors.initials: M
authors.lastname: Haugen
authors.forename: Odd
authors.initials: O
authors.lastname: Vinje
authors.forename: Dag
authors.initials: D
authors.lastname: Sørskaar
authors.forename: Knut
authors.initials: K
authors.lastname: Dale
authors.forename: Thore
authors.initials: T
authors.lastname: Egeland
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Førre
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000150:complications / Q000503:physiopathology*; D015415:Biomarkers / Q000032:analysis; D015519:Bone Density; D016723:Bone Remodeling; D002648:Child; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D010024:Osteoporosis / Q000209:etiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016474:Weight-Bearing
chemical_list: D015415:Biomarkers