What is the appropriate diagnosis and treatment for a patient presenting with bilateral polyarticular pain, considering potential underlying conditions such as rheumatoid arthritis, osteoarthritis, or lupus?

Bilateral Polyarticular Pain: Diagnostic and Treatment Approach

Begin by determining whether the pain is inflammatory or noninflammatory through assessment of joint warmth, swelling, morning stiffness duration (>1 hour suggests inflammatory), and systemic symptoms, as this fundamentally divides the diagnostic pathway. 1, 2

Initial Clinical Assessment

Key Distinguishing Features to Evaluate

• Inflammatory characteristics: Palpable synovitis, warm/swollen joints, prolonged morning stiffness (>1 hour), systemic symptoms (fever, weight loss, fatigue) point toward inflammatory arthritis 1, 2
• Noninflammatory characteristics: Variable onset, <1 hour morning stiffness, pain worsened by activity and improved by rest, bony hypertrophy and crepitus on examination suggest osteoarthritis 3
• Joint distribution pattern: Note which specific joints are affected (DIPs, PIPs, MCPs, wrists) and whether involvement is symmetric or asymmetric 4
• Age and demographics: Onset after age 40 with DIP/PIP involvement suggests osteoarthritis; younger patients with MCP/PIP/wrist involvement suggest rheumatoid arthritis 4

Differential Diagnosis by Pattern

Inflammatory Polyarthritis (Warm, Swollen Joints, Prolonged Stiffness)

Primary considerations:

• Rheumatoid arthritis: Symmetric involvement of MCPs, PIPs, and wrists; spare DIPs 4, 5
• Psoriatic arthritis: May target DIPs or affect single rays; look for skin/nail changes 4, 5
• Systemic lupus erythematosus: Consider in patients with autoimmune history and systemic features 5
• Gout: Can superimpose on pre-existing osteoarthritis; may present as polyarticular symmetric tophi 4, 6
• Viral arthritis: Acute, self-limited presentation 1

Noninflammatory Polyarthritis (Bony Changes, Minimal Stiffness)

Primary consideration:

• Osteoarthritis: Targets DIPs (Heberden nodes), PIPs (Bouchard nodes), thumb base, and index/middle MCPs; associated with age >40, female sex, obesity 4
• Erosive hand osteoarthritis: Abrupt onset with inflammatory features (stiffness, swelling, erythema), targets IPJs, may have mildly elevated CRP 4

Diagnostic Workup

Laboratory Testing

Order selectively based on clinical suspicion:

• If inflammatory arthritis suspected: CBC, CRP/ESR, rheumatoid factor, anti-CCP antibodies for rheumatoid arthritis 2
• If atypical features present: Blood tests to screen for psoriatic arthritis, gout (uric acid), hemochromatosis (iron studies), lupus (ANA, complement levels) 4, 5
• Blood tests are NOT required for osteoarthritis diagnosis but may exclude coexistent inflammatory disease 4

Imaging

Plain radiographs are the initial and often sufficient imaging modality:

• For hand involvement: Posteroanterior radiograph of both hands on single film shows joint space narrowing, osteophytes, subchondral sclerosis/cysts (osteoarthritis) or erosions (erosive OA, rheumatoid arthritis) 4
• MRI is reserved for cases where radiographs are equivocal or when assessing for early inflammatory changes not yet visible on plain films 2

Joint Aspiration

Perform when infection or crystal arthropathy is considered:

• Synovial fluid analysis for cell count, crystals (monosodium urate for gout, calcium pyrophosphate for pseudogout), and culture 5, 6

Treatment Approach

For Inflammatory Polyarthritis (Rheumatoid Arthritis Pattern)

Initiate disease-modifying therapy promptly to prevent joint damage:

• First-line: Methotrexate 7.5 mg orally once weekly for adults, or 10 mg/m² weekly for polyarticular juvenile arthritis 7
• Adjunctive therapy: NSAIDs and/or low-dose corticosteroids may continue during methotrexate initiation 7
• Monitoring requirements: CBC, hepatic function, renal function, and pulmonary assessment before starting and periodically during therapy 7
• Dosage adjustment: May gradually increase to achieve optimal response; adult doses >20 mg/week significantly increase toxicity risk 7
• Expected response: Clinical improvement typically begins within 3-6 weeks, with continued improvement for 12+ weeks 7

Common pitfall: Delaying DMARD therapy while attempting prolonged NSAID-only treatment leads to irreversible joint damage 7

For Noninflammatory Polyarthritis (Osteoarthritis)

Focus on symptomatic management and function preservation:

• NSAIDs for pain control 8
• Physical therapy and activity modification 4
• Intra-articular corticosteroid injections for severely symptomatic joints 8

For Erosive Hand Osteoarthritis

Treat more aggressively given inflammatory component:

• NSAIDs and corticosteroids for inflammatory symptoms 8
• Consider DMARDs if severe, though evidence is limited 8

Critical Considerations

Assess for generalized osteoarthritis: Patients with polyarticular hand OA are at increased risk for knee, hip, and other joint involvement; examine accordingly 4

Functional impairment in hand OA can equal that of rheumatoid arthritis: Use validated outcome measures to monitor function 4

Septic arthritis exclusion: Joint aspiration is mandatory when infection is considered, as this is a medical emergency requiring immediate treatment 4