title: Prevalence of HLA-B27 antigen in patients with juvenile idiopathic arthritis.
abstract: BACKGROUND
  Human leukocyte antigen B27 (HLA-B27) is considered as a risk factor for development of juvenile idiopathic arthritis (JIA). The aim of this study was to analyse the prevalence of HLA-B27 antigen in JIA categories and its influence on disease onset and response to conventional therapy.
  
  
  METHODS
  The retrospective analysis included 461 unselected children with JIA hospitalized in a single reference rheumatology centre between July 2007 and June 2012. The diagnosis was based on criteria by the International League of Association for Rheumatology. HLA-B27 was determined in 387 of all patients (84%) by hybridization of the amplified, labelled product to immobilize it on the microarray probe.
  
  
  RESULTS
  HLA-B27 antigen was found in 104 of 383 affected children (27.2%), 48 of 206 girls (23.3%), and 56 of 177 boys (31.6%) - most frequently in patients with enthesitis-related arthritis (71%), psoriatic arthritis (50%) and unclassified cases (86.7%). The age of JIA onset was slightly (by 1 year) but significantly different in patients with and without HLA-B27 antigen [11 (8.5-14) vs. 10 (5-13.5) years.; p < 0.001]. The use of disease-modifying antirheumatic drugs (DMARDs) and corticosteroids was more frequently clinically ineffective in HLA-B27 positive than negative patients (23.1% vs. 15.2%; p = 0.09). Patients with polyarthritis, systemic, and psoriatic arthritis more frequently received biological therapy. HLA-B27 positive patients with enthesitis-related arthritis received biological therapy more frequently than HLA-B27 negative ones (20.4% vs. 0, respectively; p = 0.09).
  
  
  CONCLUSIONS
  HLA-B27 antigen is a strong risk factor for the development of enthesitis-related arthritis, and to a lesser extent for psoriatic arthritis and extended course of oligoarthritis. The presence of this antigen does not affect the disease onset but seems to predict resistance to therapy with disease-modifying drugs and corticosteroids.
authors.affiliation: Department of Older Children with Subwards of Rheumatology, Neurology and Rehabilitation, St. Louis Children's Hospital, Krakow, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Żuber
authors.affiliation: Department of Older Children with Subwards of Rheumatology, Neurology and Rehabilitation, St. Louis Children's Hospital, Krakow, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Turowska-Heydel
authors.affiliation: Department of Older Children with Subwards of Rheumatology, Neurology and Rehabilitation, St. Louis Children's Hospital, Krakow, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Sobczyk
authors.affiliation: Chair of Pathophysiology, Medical Faculty in Katowice, Medical University of Silesia, Katowice, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Chudek
keywords: HLA-B27 antigen; juvenile idiopathic arthritis; therapy