title: Ankle arthritis predicts polyarticular disease course and unfavourable outcome in children with juvenile idiopathic arthritis.
abstract: OBJECTIVE
  To evaluate the occurrence, clinical characteristics and prognostic factors associated with ankle arthritis in children with juvenile idiopathic arthritis (JIA).
  
  
  METHODS
  440 children with JIA were followed for eight years in a prospective Nordic population-based cohort study. Data on remission was available for 427 of these children. Occurrence of clinically assessed ankle arthritis was analysed in relation to JIA category, clinical characteristics and remission data eight years after disease onset.
  
  
  RESULTS
  In 440 children with JIA, 251 (57%) experienced ankle arthritis during the first eight years of disease. Ankle arthritis was least common in the persistent oligoarticular category (25%) and most common in children with extended oligoarticular (83%) and polyarticular RF-negative (85%) JIA. Children who developed ankle arthritis during the first year of disease were younger at disease onset (median age 4.9 (IQR 2.1-8.8) vs. 6.6 (IQR 2.8-10.1) years, p<0.003) and had more cumulative affected joints at 8-year follow-up (median involved joints 10 (IQR 6-16) vs. 3 (IQR 2-9), p<0.001). The odds ratio for not achieving remission eight years after disease onset, if the ankle joint was involved during the first year of disease was 2.0 (95 % CI:1.3-3.0, p<0.001). Hind-, mid- and forefoot involvements were more common compared to patients without ankle arthritis.
  
  
  CONCLUSIONS
  In this Nordic population-based 8-year follow-up study, occurrence of ankle arthritis during the first year was associated with an unfavourable disease outcome. We suggest that ankle arthritis should be recognised in the assessment of prognosis and choice of treatment strategy in JIA.
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anna-Clara
authors.initials: AC
authors.lastname: Esbjörnsson
authors.affiliation: Department of Paediatrics, Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Finland.
authors.forename: Kristiina
authors.initials: K
authors.lastname: Aalto
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Eva W
authors.initials: EW
authors.lastname: Broström
authors.affiliation: Department of Paediatrics, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Fasth
authors.affiliation: Department of Paediatrics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Herlin
authors.affiliation: Paediatric Rheumatology Department, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Susan
authors.initials: S
authors.lastname: Nielsen
authors.affiliation: Department of Paediatrics, University Hospital of North Norway and Institute of Clinical Medicine, UIT the Arctic University of Norway, Tromsø, Norway.
authors.forename: Ellen
authors.initials: E
authors.lastname: Nordal
authors.affiliation: Department of Paediatrics, Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Finland.
authors.forename: Suvi
authors.initials: S
authors.lastname: Peltoniemi
authors.affiliation: Department of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology and Department of Paediatrics, St. Olavs Hospital, Trondheim, Norway.
authors.forename: Marite
authors.initials: M
authors.lastname: Rygg
authors.affiliation: Paediatric Rheumatology Department, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Marek
authors.initials: M
authors.lastname: Zak
authors.affiliation: Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Lillemor
authors.initials: L
authors.lastname: Berntson
mesh_terms: D017668:Age of Onset; D000843:Ankle Joint; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001171:Arthritis, Juvenile / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D010003:Osteoarthritis / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012074:Remission Induction; D012189:Retrospective Studies; D012307:Risk Factors; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018501:Antirheumatic Agents