Juvenile Chronic/Idiopathic Arthritis (JCA) (Juvenile rheumatoid arthritis)
Heterogenous group of rheumatic disease in children, first described by Still in 1897. Literature is confusing on terminology – often used interchangeably with ‘juvenile rheumatoid arthritis’. Difficult to diagnose (variety of presentations) - no definitive diagnostic test. Diagnosis is usually reserved for those who are under are age of 16 at onset – affects about 1 in 1000. Characterised by peripheral synovitis with soft tissue effusions and swellings.
ARA criteria for diagnosis:
1. Chronic synovial inflammation of unknown origin
2. Onset in children less than 16 years of age
3. Objective evidence of arthritis in one or more joints for 6 consecutive weeks
4. Exclusion of other disease
3 main types of JCA (based on clinical presentations, with various amounts of overlap):
1. Pauciarticular (<5 joints) or monarticular (50% of JCA’s; gradual onset of joint pain – most commonly the knee – usually asymmetric; eye complications are common; other systemic complications absent; peak age of onset 2-5yrs; F>M; another group is more common in males with age of onset > 6yr – M>F)
2. Polyarticular (40% of JCA’s; usually around 10 years; F>M; joint symptoms predominate – usually symmetric; systemic upset mild; have ‘flare ups’) – 10% of these develop a form the same as the adult onset rheumatoid arthritis
3. Systemic (Still’s disease) (10% of JCA’s; usually ages 1-5; acutely ill; usually have recurrent attacks of high fever with minimal joint damage; skin rashes common; joint inflammation is not common initially – polyarticular course)
Enthesitis-related Arthritis (ERA)
Pain at sites of insertion of tendons and ligaments into bone- usually need to also have sacroiliac tenderness and HLA-B27- can have family history of HLA-B27 associated spurdyloarthropathy.
Onset can be severe enthosopathy of heels .
Aetiology – unknown; some HLA subtypes have been identified; certain viruses have been implicated as triggers
Adults who had juvenile chronic arthritis have 4 times the mortality rate compared to a control population (French et al, 2001)
Other inflammatory joint conditions (eg gout); infections arthritis; Lyme disease; transient synovitis of hip; acute rheumatic fever; past infections; serum sickness
Foot joints can be frequently affected . Inflammation of ankle and small foot joints will lead to alignment deformities in the joints and affect foot biomechanics – especially ankle equinus and subtalar varus or valgus. Can result in flexion contractures of hip, knee and ankle as well as leg length discrepancies. Synovitis of the subtalar joint is common and is responsive to intraarticular cortisone .
Plantar pressure measurements have shown reduced toe and medial metatarsal head weightbearing and increased lateral metatarsal head weightbearing .
On foot x-ray, often see an enlargement and irregularity of tarsal bones – joint space narrowing and joint ankylosis is also common.