Juvenile Idiopathic Arthritis

Persistent oligo- or polyarthritis in a child <16 years with no clear underlying cause, lasting months to years.

Oligoarthritis (≤4 joints)

• Usually presents age 1–4; girls > boys.
• Typically knees, ankles, wrists, elbows — hips rarely involved.
• ~70% ANA-positive; rarely rheumatoid factor positive.
• Associated with anterior uveitis — needs regular ophthalmology screening.

Polyarthritis (≥5 joints)

• Typically age 2–4; girls 2× boys.
• Asymmetrical, large and small joint involvement; commonly involves the hips.
• Anterior uveitis can occur, but less commonly than in oligoarthritis.

Systemic arthritis (Still disease)

Children are generally unwell, with spiking fevers twice daily, generalised rash, generalised lymphadenopathy, hepatosplenomegaly, peritonitis, pericarditis. Will usually look sick — admit to hospital.