Background/Purpose: Down’s Arthritis (DA) was first reported in the literature in 1984. Crude estimates suggest higher incidence and prevalence rates of DA compared with Juvenile Idiopathic Arthritis (JIA), (JIA prevalence 1/1000, estimated DA prevalence 8.7/1000). Despite this fact, there remains a paucity of data on this condition. DA is rarely recognised at onset, & remains under-diagnosed. As a direct consequence children with DA are presenting with significant joint damage and disability at diagnosis. Our aim was to perform a musculoskeletal examination on children with Trisomy 21 (T21) aged 0-20 years, looking specifically for features of undiagnosed arthritis. We also wanted to better define the disease in terms of it’s clinical and radiological features.

Methods: Children with T21 were invited to attend a screening clinic. Screening involved completion of a health questionnaire and a comprehensive musculoskeletal examination. DA cases detected were investigated & managed as per normal clinical practice. Data on a convenience sample of 33 newly diagnosed children with JIA was collected to create a comparison group.

Results: 503 children with T21 were screened for DA and 22 new cases identified. All of these children had poor language skills or were non-verbal. Only 11% of the parents suspected that their child may have arthritis prior to attending our screening clinics, and this was only after reading our recruitment literature. In total, we now have 33 children attending our centre with DA (combining cases attending pre-dating the start date of the study). This suggests the prevalence of DA in Ireland is 18-21/1000.

The majority of children presented with a polyarticular RF negative pattern of disease. No cases of uveitis have been observed to date. Small joint involvement of the hands was observed in 88% of the DA cohort, significantly higher than in the JIA comparison group (43%, p<0.01). Erosive changes were reported on X-Ray in 29.2% of the DA cohort (9.5% in the JIA Cohort). Methotrexate-associated nausea was a significant barrier to treatment with this DMARD in DA. There was a significant delay in diagnosis of DA, 1.7 years (0.2-4.9yrs) versus 0.7 years (0..2-2.4yrs) in the JIA cohort.

Conclusion: Children with T21 are at increased risk of developing arthritis. There is a lack of awareness of this risk among health care professionals & the general public at large. This almost certainly contributes to poor recognition of the disease and a delay in diagnosis. The predominant pattern of disease is polyarticular small joint arthritis. Treatment with standard protocols used in JIA is complicated by drug-associated side effects in children with T21. However, a good response to treatment with steroid intra-articular joint injections and anti-TNF therapy has been observed. Our study has raised a number of questions. Our on-going research aims to accurately define this disease in terms of its immunological, histopathological and genetic basis, & identify best practice with regards to treatment. We advocate that all children with T21 should have an annual musculoskeletal examination as part of their health surveillance programme.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/downs-arthritis-da-clinical-and-radiological-features-of-arthritis-in-children-with-trisomy-21/