P174 HLA B27 status and disease phenotype: a cohort study of 223 patients with enthesitis-related arthritis

Abstract

Abstract Background/Aims Enthesitis-related arthritis (ERA) is a subtype of juvenile idiopathic arthritis (JIA) accounting for 10-20% of patients with JIA. ERA is associated with a poor prognosis compared to other JIA subtypes. Whilst a high proportion of patients with ERA are HLA-B27 positive, the correlation between HLA-B27 status and disease phenotype is not well described. The aim of our study was to investigate the influence of HLA-B27 status on ERA phenotype. Methods Demographic and clinical data were collected and HLA-B27 positive and negative patients were compared. All subjects included met ILAR classification criteria. The data were analysed using R software (R version 4.0.4). Median and interquartile range (IQR) were calculated for continuous variables and frequency and percentage for categorical variables. Subgroup comparison was performed using the chi-squared test for qualitative variables, and Wilcoxon rank-sum for quantitative variables. P values less than 0.05 were considered significant. Results 223 patients were included in this study. The median age of symptom onset was 12 years (IQR: 9-14). The median disease duration was 11 years (IQR: 7-14). 18% of patients had family history of HLA-B27-related disease and 67% had positive HLA-B27. 54% of patients were on conventional disease modifying anti-rheumatic drugs (cDMARDs). 80% were on biologic DMARDs (bDMARD). HLA-B27 positive patients (n = 148) and negative patients (n = 68) were compared. Our analysis revealed a higher proportion of male patients in the HLA-B27 positive cohort (74% [n = 111] versus 59% [n = 39], p = 0.02). HLA-B27 positive subjects developed ERA at an older age compared to the HLA-B27 negative group at 12 versus 11 years, respectively (p = 0.02). HLA-B27 positive patients also had a higher probability of an axial phenotype within 12 months of disease onset 51% (n = 75) in the HLA-B27 positive group versus 32% (n = 22) in the HLA-B27 negative group (p = 0.01). At any point of disease course, sacroiliitis was also more common in the HLA-B27 positive group (78% [n = 116] versus 63% [n = 43], p = 0.01), who also had a higher usage of bDMARDS (74% [n = 110] versus 56% [n = 38], p = 0.006). There was no significant difference between the two groups in terms of ethnicity, family history of HLA-B27 disease or the prevalence of extra-articular manifestations, including uveitis. Conclusion Our study revealed that patients with ERA who were HLA-B27 positive, were more likely to be male, developed disease at an older age and had a higher probability of axial phenotype at onset and later in disease. They also had an increased bDMARD requirement. These data suggest that HLA-B27 confers a worse prognosis clinically which is consistent with findings from other studies. Disclosure A. Bouraoui: None. C. Fisher: None. J. Glanville: None. D. Sen: None.