AB0223 Trisomy 21 and Juvenile Idiopathic Arthritis: Are There Differences in Joint Distribution Patterns and Response to Methotrexate?

Background Children with trisomy 21 have an increased risk of developing polyarticular arthritis. Traditionally, these patients receive a diagnosis of juvenile idiopathic arthritis (JIA) and are treated accordingly. However, very little data exists regarding presentation and treatment response in these patients. Objectives To determine joint activity and distribution pattern in patients with trisomy 21 and JIA and their response to methotrexate compared to patients with seronegative polyarticular JIA. Methods Retrospective case-control study from database of the German Center for Pediatric and Adolescent Rheumatology. Patients with trisomy 21 (T21, confirmed by karyotyping) and JIA were searched including patients with visits within the last 5 years. As a control group two randomly selected patients with rheumatoid-factor negative polyarticular JIA (SNP-JIA) matching with age and gender were extracted for each T21-patient. A retrospective chart survey was used to extract the following data: affected joints at any time and first visit, extraarticular manifestations, and for patients with polyarticular disease: total joint count. As these data result from a historical database only erythrocyte sedimentation rate, adverse events and total active joint count (TJC) at initiation and 1 year after start of Methotrexate were used to determine the response to MTX. Analyses were performed using descriptive statistics, Spearman9s correlation to compare response to methotrexate. Results 11 T21 patients were included in the study (6 female/5 male), with a median age at diagnosis of 6 years (range 1-13 years). Median follow-up was 6 years (range 1-17 years). 9/11 (82%) showed a polyarticular course of arthritis, and all of these were treated with methotrexate. There was no different prevalence of adverse events under MTX in both groups. T21 patients with SNP-JIA showed a significantly higher total joint count of active and painful arthritis at time of diagnosis (mean, n=27) compared with SNP-JIA patients (mean, n=15,5). Initially 8 of 11 (73%) T21-JIA patients presented with SNP-JIA, which is a not expected distribution in ILAR subgroups (expected percentage: SNP 13 -15%). One T21 patient had S-JIA and two an extended Oligo-JIA. Follow up shows a decreased range of motion in at least one joint in more than 81% of T21-JIA patients. We found a significantly higher rate of hypothyreosis in T21 JIA patients (73%) than in Down–syndrome overall (35%). Notably there was no T21-JIA patient with JIA associated uveitis. Conclusions There is a difference in distribution of subtypes of JIA in trisomy-21 patients with a predominant polyarticular pattern. T21-JIA patients show a significantly higher joint count of active arthritis at time of diagnosis and a decreased range of motion in course of the disease, but no difference in MTX tolerance as compared to SNP-JIA patients. Therefore we propose the early initiation of MTX as efficacious and safe therapy, in patients with Trisomy 21 and Juvenile Idiopathic Arthritis. Disclosure of Interest None declared