Down syndrome-associated arthritis (DA) is an aggressive, erosive, inflammatory arthritis that affects one in 50 children with Down syndrome.

Up until now there was little information on its unique immunological features, which hindered effective treatment.

New research led by Molecular Rheumatology, Trinity Biomedical Sciences Institute, TCD; with the National Children’s Hospital Crumlin; and St Vincent's University Hospital, UCD, have identified an underlying immune system dysregulation in children with Down syndrome-associated arthritis that is distinct from that of juvenile idiopathic arthritis (JIA).

This is the first detailed study to examine immune cell responses in these children, which demonstrated that a specific cell type of the immune system is significantly activated in children with DA, resulting in increased joint inflammation. The altered immune profile observed in children with DA was associated with a more aggressive, erosive and damaging form of arthritis, emphasizing the need for early diagnoses.

This work represents a significant advance in our understanding of the underlying mechanisms involved in driving this inflammatory form of arthritis. As highlighted, Down syndrome-associated arthritis is potentially more aggressive than JIA which affects one in 1,000 children.

Furthermore, the lack of awareness of increased risk of arthritis in children with Down syndrome, suggests this group is potentially at a greater risk of long-term complications. Further studies and support for this condition, will lead to improved diagnostic and prognostic outcomes for patients.

This research was published in the international peer-reviewed journal ‘Arthritis & Rheumatology’*, and was funded by Arthritis Ireland, Down Syndrome Ireland, the National Children’s Research Centre Crumlin and the Health Research Board.

*Foley C, Floudas A, Canavan M, Biniecka M, MacDermott EJ, Veale DJ, Mullan RH, Killeen OG, Fearon U.

Increased T cell plasticity with dysregulation of T follicular helper, T peripheral helper and T regulatory cell responses in children with JIA and Down syndrome-associated arthritis. Arthritis Rheumatol. 2019 Oct 27.