Juvenile chronic arthritis

Question 1

JIA (juvenile idiopathic arthritis) - background

Answer 1

1. Definition = persistent joint swelling >6 weeks presenting before 16y in the absence of infection or any other defined cause
2. 95% of children have a disease that is clinically and immunogenetically distinct from RA in adults. Typically starts any time after 1yo
3. Commonest chronic inflammatory joint disease in children and adolescents (UK), prevalence 1:1000
4. Divided into 7 subsets for research categories; not diagnostic, but useful for clinical groups
5. As a child’s symptoms evolve with time (e.g. the appearance of a psoriatic rash), they may change subtypes

Question 2

JIA - classification

Answer 2

1. Systemic arthritis, acute illness with malaise and high daily fever initially (10-13%)
2. Oligoarthritis, 1-4 joints (40%)
3. Polyarthritis (rheumatoid factor +ve) (3%)
4. Polyarthritis (rheumatoid factor -ve) (27%)
5. Psoriatic arthritis (2-15%)
6. Enthesitis-related (1-7%)
7. Undifferentiated arthritis (2-15%)

Question 3

JIA - symptoms

Answer 3

1. Gelling (stiffness after periods of rest, e.g. long car rides)
2. Morning joint stiffness
3. Pain

Young child

4. Intermittent limp
5. Deterioration in behaviour or mood, or avoidance of previously enjoyed activities (rather than complaining of pain)

Note: before labelling the child with a dx of JIA, it is imperative to exclude the ddx of sepsis, trauma and malignancy.

Question 4

JIA - signs

Answer 4

Initially

1. Joint effusion
2. Synovitis/proliferation and thickening of synovium (?)
3. Swelling of periarticular soft-tissues

Long-term
4. Leg length discrepancy/valgus deformity if knee affected
5. Digit length
discrepancy if hands affected

Distinguishing between types:

1. Systemic JIA -> fever, salmon-coloured evanescent rash
2. Polyarticular JIA -> symmetrical joint involvement, >4 joints
3. Oligoarticular JIA -> fewer than five joints affected
4. Psoriatic JIA -> skin and nail disease (psoriasis)
5. Enthesitis-related JIA -> enthesitis, axial symptoms, positive family history of spondylitis

Question 5

JIA - complications

Answer 5

1. Chronic anterior uveitis - common but asymptomatic and can lead to severe visual impairment
2. Flexion contractures of joints - occur when joint is held in most comfortable position (minimising intra-articular pressure) -> if untx, can lead to joint destruction and the need for joint replacement
3. Growth failure (from anorexia, chronic disease and systemic corticosteroid therapy) + localised overgrowth (e.g. leg length discrepancy due to prolonged active knee synovitis)
4. Constitutional problems - anaemia of chronic disease, delayed puberty
5. Osteoporosis - etiology = diet, reduced weight bearing, systemic corticosteroids and delayed menarche

Question 6

JIA - ix

Answer 6

1. Bloods (5) = FBE, ESR, CRP, rheumatoid factor, ANA (but ANA non-specific)
2. Infection screen (if rash?) = throat swab, urinalysis, blood for ASOT, viral serology (CMV, EBV, parvovirus B19, hepatitis), culture
3. X-rays - to exclude fracture or tumour. Early = soft-tissue swelling and juxta-articular osteopenia. Later = joint space narrowing and erosions
4. U/S - helpful for confirming synovitis and joint effusion. MRI - for atypical monoarthritis
5. Synovial fluid aspirate - culture for sepsis

Question 7

JIA - mx

Answer 7

1. NSAIDs (initially, e.g. naproxen, indomethacin)

2. Intra-articular corticosteroid therapy under GA in child

Question 8

JIA - prognosis (3)

Answer 8

1. 1 in 3 have ongoing active disease into adult years
2. Morbidity - joint damage requiring joint replacmement surgery, visual impairment from uveitis, fractures from osteoporosis
3. Psychosocial morbidity