Arthropathy of Down syndrome: an under-diagnosed inflammatory joint disease that warrants a name change.

Unlabelled: There is an increased incidence and prevalence of arthropathy in children with Down syndrome. However, it is rarely reported or recognised at onset, and remains under-diagnosed. Children with arthropathy of Down syndrome (A-DS) are presenting with significant joint damage and disability at diagnosis.

Objective: To identify undiagnosed cases of A-DS and document time to diagnosis. Also to describe clinical, laboratory and radiological features of A-DS at diagnosis.

Methodology: Children with Down syndrome (DS) (0-21 years) were invited to attend a musculoskeletal screening clinic. A second physician at a further clinic confirmed suspected cases of A-DS. Investigations and treatment were instigated as per normal clinical practice for Juvenile idiopathic arthritis (JIA). Data on a convenience sample of 21 newly diagnosed children with JIA was collected to create a comparison group.

Results: Over an 18-month period, 503 children with DS were screened for arthritis and 18 new cases diagnosed. In total, 33 children were identified with A-DS (combining cases attending pre-dating commencement of the study and those referred to our centre during the study period). This suggests prevalence of A-DS is 20/1000. A significant delay in diagnosis of A-DS was observed. The majority of children presented with polyarticular-rheumatoid factor-negative arthritis, with predominance in the small joints of the hands and wrists. Erosive changes were reported on X-ray in a significantly greater proportion (42%) of children with A-DS than JIA (14%). MRI was used to confirm diagnosis in four cases.

Conclusion: Children with DS are at increased risk of arthritis. Future research to accurately define disease pathogenesis and identify a biomarker of disease would be of benefit.