title: Juvenile idiopathic arthritis classified by the ILAR criteria: HLA associations in UK patients.
abstract: OBJECTIVE
  To determine the HLA associations with juvenile idiopathic arthritis (JIA) and its subgroups as defined by the International League of Associations for Rheumatology (ILAR) classification criteria.
  
  
  METHODS
  Five hundred and twenty-one UK Caucasian JIA patients and 537 UK Caucasian controls were typed for HLA class II alleles. Phenotype and haplotype frequencies were compared between all JIA cases and controls and between the seven ILAR-defined JIA subgroups.
  
  
  RESULTS
  Three haplotypes (DRB1*08-DQA1*0401-DQB1*0402; DRB1*11-DQA1*05-DQB1*03; DRB1*1301-DQA1*01-DQB1*06) were associated with increased risk and one (DRB1*04-DQA1*03-DQB1*03) with decreased risk of JIA. However, in each case the frequencies also varied between JIA subgroups.
  
  
  CONCLUSIONS
  This study categorically demonstrates that there are multiple HLA class II associations with JIA. It has also, for the first time, defined these associations in the seven different ILAR subgroups in UK JIA cases. Although there are a number of common associations, each ILAR subgroup exhibits different patterns of HLA associations, suggesting that the ILAR classification system does define genetically distinct groups of patients.
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000145:classification / Q000453:epidemiology / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D015796:HLA-B27 Antigen / Q000235:genetics; D006681:HLA-D Antigens / Q000235:genetics*; D006682:HLA-DP Antigens / Q000235:genetics; D059868:HLA-DP beta-Chains; D006683:HLA-DQ Antigens / Q000235:genetics; D006684:HLA-DR Antigens / Q000235:genetics; D059811:HLA-DRB1 Chains; D006239:Haplotypes; D006801:Humans; D007223:Infant; D008297:Male; D010641:Phenotype; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D015796:HLA-B27 Antigen; D006681:HLA-D Antigens; D006682:HLA-DP Antigens; D059868:HLA-DP beta-Chains; C071170:HLA-DPB1 antigen; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains