Rheumatoid arthritis

Overview

•Symmetrical polyarthritis - MCP, PIP, and wrist joints most commonly; DIP joints typically spared

•Morning stiffness - lasting >1 hour, improves with activity (reflects active synovial inflammation)

•Systemic features - fatigue, malaise, low-grade fever

•Hand deformities (late disease) - ulnar deviation at MCPs, swan-neck (PIP hyperextension + DIP flexion), boutonnière (PIP flexion + DIP hyperextension), Z-deformity of thumb

RA vs OA - key distinguishing features
FeatureRheumatoid arthritisOsteoarthritis
Morning stiffness>1 hour, improves with activityFew minutes, worsens with activity
Joints affectedMCP, PIP, wrist (DIP spared)DIP, CMC, knee (MCP/PIP less common)
DistributionSymmetrical polyarthritisAsymmetrical, weight-bearing joints
X-ray: specific findingsPeriarticular erosions, juxta-articular osteoporosis, soft tissue swellingOsteophytes, subchondral sclerosis, subchondral cysts
Hand signSwan-neck, boutonnière, ulnar deviationSquaring of thumb (CMC subluxation)

Feature	Rheumatoid arthritis	Osteoarthritis
Morning stiffness	>1 hour, improves with activity	Few minutes, worsens with activity
Joints affected	MCP, PIP, wrist (DIP spared)	DIP, CMC, knee (MCP/PIP less common)
Distribution	Symmetrical polyarthritis	Asymmetrical, weight-bearing joints
X-ray: specific findings	Periarticular erosions, juxta-articular osteoporosis, soft tissue swelling	Osteophytes, subchondral sclerosis, subchondral cysts
Hand sign	Swan-neck, boutonnière, ulnar deviation	Squaring of thumb (CMC subluxation)

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DIP joint involvement favours OA or psoriatic arthritis - RA characteristically spares the DIPs. Psoriatic arthritis also causes dactylitis ('sausage digit') and nail changes, and can present as oligoarthritis before any rash appears.

Investigations

•Anti-CCP antibodies - positive in ~80% RA; specificity ~96%; most diagnostically useful serological test

•Rheumatoid factor (RF) - positive in 60-70% RA; low specificity (positive in infection, other autoimmune diseases)

•CRP and ESR - raised; correlate with disease activity

•X-rays of hands and feet - four characteristic findings: periarticular erosions (most specific/diagnostically supportive), juxta-articular osteoporosis (earliest finding), soft tissue swelling, joint space narrowing

•U&Es and LFTs - baseline before DMARDs (methotrexate is hepatotoxic; NSAIDs are nephrotoxic)

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Juxta-articular osteoporosis is the earliest and most RA-specific X-ray finding. Periarticular erosions are the most diagnostically supportive overall. Osteophytes and subchondral sclerosis point away from RA towards OA.

Management

•Treat-to-target - aim for DAS28 remission (<2.6) or low disease activity (<3.2); reassess monthly in active disease

•First-line DMARD: methotrexate - initiate ideally within 3 months of symptom onset; early treatment reduces structural damage

•Bridge therapy: NSAIDs (with PPI cover) or short-course corticosteroids while awaiting DMARD effect

•Non-pharmacological - physiotherapy, occupational therapy, podiatry, psychological support

•Annual cardiovascular risk assessment - aggressive risk factor management; IHD is the leading cause of premature death

⚠️
Raised serum ACE in a patient with polyarthritis and negative RF/anti-CCP should prompt consideration of acute sarcoidosis rather than RA.

Extra-articular features

•Cardiovascular - accelerated atherosclerosis; ischaemic heart disease is the leading cause of excess mortality in RA (approximately double the risk of the general population)

•Respiratory - pulmonary fibrosis (lower zone), pleural effusions, pulmonary nodules

•Rheumatoid nodules - firm, subcutaneous, at pressure points (e.g. olecranon); seropositive patients only

•Felty syndrome - RA + splenomegaly + neutropenia; increased infection risk

•Ophthalmic - keratoconjunctivitis sicca, episcleritis, scleritis

•Atlanto-axial subluxation - cervical myelopathy in severe longstanding disease