Paediatrics: Rheumatoid factor-positive polyarthritis

Rheumatoid factor-positive polyarthritis

A chronic symmetrical infl ammatory polyarthritis (>5 joints) with positive RF on two occasions at least 3mths apart. Typically affects teenage girls, though any age possible. Similar to adult rheumatoid arthritis, but gener-ally a more aggressive disease.

ARA criteria for diagnosis of rheumatoid arthritis¹

•   Morning stiffness: >1hr at peak illness

•   Arthritis in at least 3 joints: witnessed by a physician

•   Hand arthritis: wrists, MCPs, or PIPs

•   Symmetrical arthritis

•   Rheumatoid nodules

•   Rheumatoid factor-positive

•   Erosions on X-ray

All symptoms need to be present for at least 6wks. Four or more crite-ria need to be fulfilled for diagnosis of rheumatoid arthritis (RA). These are primarily classification criteria (90% sensitivity and specificity).

Clinical features

•   History of early morning and immobility stiffness.

•   Symmetrical arthritis affecting large and small joints associated with rheumatoid nodules. Wrists and PIPs affected early. Hip involvement can be aggressive and lead to early hip replacement.

•   Tenosynovitis common around fingers and ankles.

•   Systemic features: low grade fever (differential diagnosis systemic JIA); hepatosplenomegaly; lymphadenopathy; serositis (pericarditis and pleurisy).

•   Eyes: uveitis rare; dry eyes relatively common (10–35%); episcleritis can lead to a painful red eye.

Investigations

•   FBC; CRP; LFTs; RF; ANA.

•   Renal function and urinalysis.

•   X-rays of affected joints and CXR.

Management

•   Monitor disease activity and aim for good control of arthritis.

•   Regular meticulous assessment for tender and swollen joints, muscle wasting, joint damage, and loss of joint function.

•   Monitor growth development and nutritional status.

•   Exercise: range of joint motion and aerobic activity.

•   Psychosocial development can be severely affected and needs addressing.

Treatment

• Start treatment as soon as possible.

• NSAIDs provide relief from pain, stiffness, and swelling.

• All children will need disease-modifying antirheumatic drug (DMARDs): MTX is the least toxic and most well established—orally or SC. Others include hydroxychloroquine, sulfasalazine, azathioprine, ciclosporin, and gold. These have been used in combination with MTX or alone.

• Steroids: intra-articular steroids to settle synovitis in individual joints; oral steroids as adjunct to DMARDs; pulsed IV steroids for flare of disease. Aim to minimize total steroid load.

• Biologic agents: Anti-TNF agents (etenercept, infliximab, adalimimab) have been shown to reduce joint erosions and may prevent progression to secondary arthritis