Downs syndrome - Trisomy 21. Musculoskeletal features are common:
- General hypotonia ('floppy baby').
- Cervical spine instability.
- Hip dislocation/subluxation.
- Short stature.
Inflammatory arthritis and Downs syndrome:
- Down's Arthritis is approximately 20 times more common than JIA in the general paediatric population.
- There needs to be a high index of suspicion of arthritis when assessing a child with Downs syndrome presenting with behavioural change and/or deterioration in function and mobility.
- Small joints, wrists and knees are the most commonly affected sites.
- Down’s Arthritis may often be insidious and seemingly 'asymptomatic'.
- A child with Down’s Arthritis may present with minimal clinical signs (i.e., no apparent joint pain, minimal joint swelling or early morning stiffness).
- Look for subtle signs from clinical examination that may suggest a possible diagnosis of Down’s Arthritis, e.g., loss of range or loss of hyperextension, especially if there is asymmetry between both sides. This may suggest restrictions from undiagnosed/untreated Down’s Arthritis.
- MRI with gadolinium contrast should be the 'gold standard' for definitive diagnosis of Down’s Arthritis. Consider MRI if arthritis is suspected as clinically there can be little to aid with diagnosis.
- Methotrexate intolerance is a significant barrier as a treatment for Down’s Arthritis. When required, anti-TNF medication should be considered.
- Children with Downs syndrome should have a musculoskeletal assessment (pGALS as a minimum) as part of their Annual Surveillance Programme.
- Uveitis risk is low in this patient cohort, and Rheumatoid Factor is invariably negative.
The photograph below shows joint restriction and swelling of the hands and wrists in a child with Downs syndrome and arthritis.
Please look at the videos which demonstrate a young child with Downs syndrome arthritis - the first clip demonstrates difficulty walking down the stairs with widespread joint involvement and also non-verbal signals of discomfort (e.g., facial expression and effect). The second clip shows the same child following treatment with considerable improvement.