Urgent Rheumatology Referral and Immediate Diagnostic Workup Required

This 35-year-old patient with persistent monoarticular joint pain, redness, and swelling in the left index finger for months requires immediate rheumatology referral within 6 weeks and comprehensive workup to differentiate inflammatory arthritis from infection, crystal arthropathy, or early rheumatoid arthritis. 1, 2

Immediate Clinical Assessment

Perform a focused joint examination to detect definite clinical synovitis (soft, boggy swelling from synovial inflammation rather than hard bony enlargement), assess for warmth, erythema, and tenderness, and document morning stiffness duration—stiffness lasting >30 minutes strongly suggests inflammatory arthritis. 1, 2, 3

Key Examination Findings to Document

Squeeze test across the metacarpophalangeal (MCP) joints and proximal interphalangeal (PIP) joints to detect small joint synovitis, even if the primary complaint is the index finger. 2, 4
Assess for symmetric involvement of other small joints (MCPs, PIPs, wrists, metatarsophalangeal joints), as rheumatoid arthritis characteristically presents with symmetric polyarthritis, though monoarticular presentation occurs in 25% of cases initially. 5, 3, 6
Examine for skin changes including psoriatic plaques or nail pitting (psoriatic arthritis), tophi (gout), or rheumatoid nodules. 5
Document range of motion limitation and functional impairment in the affected finger. 6

Essential Laboratory Workup

First-Line Inflammatory and Autoimmune Testing

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) for diagnostic and prognostic information—markedly elevated markers (CRP >10 mg/L, ESR >30 mm/hr) strongly suggest inflammatory arthritis, though normal values do not exclude it. 1, 2, 3
Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA/anti-CCP) have both diagnostic and prognostic value, with ACPA having high specificity (90%) and moderate sensitivity (60%) for rheumatoid arthritis. 5, 2, 3
Complete blood count with differential to identify systemic inflammation, exclude infection or malignancy, and assess for cytopenias before starting treatment. 5, 2
Comprehensive metabolic panel including liver function tests, renal function, glucose, and uric acid levels to establish baseline and exclude gout (elevated uric acid) or other metabolic causes. 5, 2
Urinalysis to identify renal involvement and exclude urinary tract infection. 5, 2

Conditional Testing Based on Clinical Presentation

Antinuclear antibodies (ANA) if diagnosis remains uncertain to screen for systemic lupus erythematosus or other connective tissue diseases. 5, 2
HLA-B27 typing if symptoms suggest reactive arthritis or spondyloarthropathy (axial or entheseal involvement). 5, 2

Imaging Studies

Baseline Radiography

Obtain plain radiographs of both hands (including the affected left index finger) to evaluate for erosions, joint space narrowing, periarticular osteopenia, or baseline structural changes—the presence of erosions predicts rheumatoid arthritis diagnosis and disease persistence. 1, 5, 2

Advanced Imaging When Diagnosis Uncertain

Ultrasound with Power Doppler is superior to clinical examination for detecting synovitis (75% more accurate than physical examination alone) and can detect subclinical inflammation that predicts disease progression even when clinical examination is equivocal. 1, 5, 2, 7
MRI with IV contrast is more sensitive than ultrasound in early stages and detects bone marrow edema (osteitis), which is the best single predictor of future disease progression and functional deterioration. 1, 5

Critical Differential Diagnoses

Inflammatory Arthritis (Most Likely)

Seronegative rheumatoid arthritis presenting with monoarticular involvement initially (occurs in 25% of cases), especially given months-long duration with persistent swelling and redness. 5, 3, 6
Psoriatic arthritis can present with monoarticular involvement including fingers, elevated inflammatory markers, and negative RF—examine carefully for psoriatic plaques or nail changes. 5

Infectious Causes (Must Exclude)

Septic arthritis or infectious tenosynovitis must be excluded urgently, particularly if there is fever, severe warmth, or rapid progression—these represent true emergencies requiring immediate drainage and antibiotics. 8

Crystal Arthropathy

Gout can affect finger joints and present with redness and swelling—check uric acid level, though normal uric acid does not exclude gout during acute flare. 5

Non-Inflammatory Causes (Less Likely)

Erosive hand osteoarthritis can present with inflammatory-like features including redness and swelling, but typically affects distal interphalangeal (DIP) joints more than proximal joints and occurs in older patients. 1, 7

Immediate Management While Awaiting Rheumatology Evaluation

Symptomatic Treatment

NSAIDs (naproxen 500 mg twice daily or meloxicam 7.5-15 mg daily) for 4-6 weeks at the minimum effective dose for the shortest duration after evaluating gastrointestinal, renal, and cardiovascular risks. 1, 9
Intra-articular corticosteroid injection can be considered for the affected finger joint if infection is excluded and NSAIDs are ineffective, though this should ideally be performed by rheumatology. 1, 2

Critical Pitfall to Avoid

Do not delay rheumatology referral or dismiss inflammatory arthritis based solely on monoarticular presentation or normal inflammatory markers—seronegative rheumatoid arthritis accounts for 20-30% of cases, acute phase reactants can be normal even in active disease, and monoarticular presentation occurs in 25% of early rheumatoid arthritis cases. 5, 3, 6