Background The heterogeneity of juvenile idiopathic arthritis (JIA) is an important topic in research and in focus for our aim to find predictive signs in patients, guiding us in research and therapy. The cell-surface antigen HLA-B27 is well known to be associated with spondyloarthropathies and associated features. In children sacroiliitis often evolves after years of arthritis in peripheral joints, which complicates classification. In the current ILAR (Edmonton) classification HLA-B27 is an important disease descriptor.
Objectives We wanted to investigate the associations of HLA-B27 on the clinical manifestation of JIA, during the first eight years of disease, in a study as close to population-based as possible. We also wanted to relate our findings to the ILAR classification.
Methods We studied an incidence-based cohort of 440 patients collected prospectively in well-defined areas in Sweden, Norway, Finland, and Denmark. Clinical and serological data of the first eight years of disease were collected.
Results HLA-B27 positive boys had significantly higher age at time of onset compared to HLA-B27 negative boys. This could not be found in girls. Signs of sacroiliitis were associated with HLA-B27 in boys but not in girls and girls with those signs were more seldom classified as enthesitis related arthritis (ERA) according to the ILAR criteria compared to boys. After a median of eight years of disease 16 girls and 33 boys were classified as ERA (11% of total cohort) and they were HLA-B27 positive in 72%. Occurrence of HLA-B27 was associated with a two times higher risk of not reaching remission off medication after eight years of disease.
Conclusions In this prospectively collected cohort of Nordic patients with JIA, followed for a median of eight years we found significant differences between HLA-B27 positive boys and girls in signs of sacroiliitis and age distribution. Classification of ERA showed differences between genders and HLA-B27 was a negative predictor for achieving remission off medication after eight years of disease.
Disclosure of Interest None Declared
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