SAT0498 ENTHESITIS-RELATED ARTHRITIS (ERA) IN SOUTHEAST ASIA: A DECADE OF SINGAPORE EXPERIENCE
Authors: T. Arkachaisri, K. L. Teh, Y. X. Book, L. Das
Journal: Annals of the Rheumatic Diseases (2020)

Background: ERA is the most common Juvenile Idiopathic Arthritis (JIA) subtype in Singapore (1), but less common in the West. Clinical characteristics and treatment of ERA in the region is not well-described thus impede the diagnosis and management plan which could lead to poorer outcomes. Objectives: To describe the clinical characteristics, joint manifestation and treatment of ERA in a large monocentric cohort in Singapore over 10-year period Methods: Children diagnosed with ERA according to ILAR criteria with a minimum follow-up of 3-month duration were recruited from our registry, from 2009 to 2019, at KK Women’s and Children’s Hospital, Singapore. Nonparametric descriptive statistics including median (IQR) were used to described data. Kaplan-Meier survival analyses were used to estimate the probability of ever sacroiliitis development. Multivariate logistic and Cox regression analyses were used to determine predictors as appropriate. The significant level was set at &lt; 0.05. Results: A cohort of 147 ERA out of 439 JIA patients (male 88%; Chinese 80%) were included. Median age at onset was 11.9 yrs (IQR9.4-14.0) and disease duration was 6.0 yrs (3.1-8.9). Median lag period was 2.9 mo (1.2-7.4). Family history of HLA-B27 related diseases was positive at 8%. Acute uveitis occurred only 3%. Joint distribution at diagnosis and cumulative involvement were shown in Fig 1. Hip, sacroiliac and knee were the three most common joints involved. 24% presented with enthesitis and Achilles tendon enthesis were the most common. Majority presented with pauciarthritis (84%) while 12% of patients had no peripheral joint involvement. 40% of patients presented with sacroiliitis (SIs) with 59% had bilateral involvement. Median duration to develop SIs was 7.6 mo (IQR 2.0-26.9). Probability of SIs development was 36%, 55% and 70% at 1, 5 and 10 yrs after onset, respectively. Interestingly, neg HLA-B27, female and older age at onset predicted SIs (p=0.001-0.044). Hip arthritis increased (p=0.043) but tarsitis decreased (p=0.031) the risk of SIs. Again, female, hip arthritis at diagnosis and neg HLA-B27 had a shorter time to SIs (p=0.004-0.007). Fig 2 showed medication used in our ERA cohort. Methotrexate (MTX) remained the most common DMARD used. However, 76% required anti-TNF therapy (aTNF) due to MTX failure. For SIs patients, 86% were on MTX but 85% of these, as compared to patients without axial disease, 60%, failed MTX. Only 10% of patients had aTNF without MTX. Fig 1. Proportion of joint involvement at onset and cumulative involvement during the course of disease (%) Fig 2. Proportion of medications used in ERA cohort during the course of disease (%) Conclusion: Our ERA cohort had less uveitis and family history of HLA-B27 associated diseases, but comparable gender and age at onset as compared to reports elsewhere(2). Up to 40% of our patients presented with SIs and/or enthesitis. Majority of SIs developed within the first 5 yrs (88%) for which over one-half developed within the first year. When considering only ERA patients, interestingly that female, neg HLA-B27 and older age increased risk of SIs development. 77% of patients were treated with MTX, but 76% of the patients required aTNF later. As for SIs, concurred with adult AS data, 85% failed MTX. About one-half of non-axial disease patients failed MTX which is less response rate as compared to other JIA subtypes. References: [1]Arkachaisri T, Tang SP, Daengsuwan T, Phongsamart G, Vilaiyuk S, Charuvanij S, et al. Paediatric rheumatology clinic population in Southeast Asia: are we different? Rheumatology. 2017;56(3):390-8. [2]Mistry RR, Patro P, Agarwal V, Misra DP. Enthesitis-related arthritis: current perspectives. Open access rheumatology: research and reviews. 2019;11:19-31. Disclosure of Interests: None declared