What is the best treatment approach for a 55-year-old woman with pain in the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints, enlarged joints, elevated erythrocyte sedimentation rate (ESR), and normal rheumatoid factor (RF), with a differential diagnosis of seronegative rheumatoid arthritis (RA) and osteoarthritis (OA)?

Diagnosis: Osteoarthritis, Not Seronegative RA

This patient has osteoarthritis based on the DIP joint involvement pattern, which is the hallmark of hand OA and essentially excludes rheumatoid arthritis. 1

Why This is Osteoarthritis

DIP joint involvement is the defining feature of hand osteoarthritis and is explicitly excluded from RA classification criteria. 1, 2 The American College of Rheumatology and European League Against Rheumatism 2010 classification criteria specifically exclude DIP joints from assessment because they are not involved in RA. 1

Key Distinguishing Features Present:

• DIP + PIP involvement = osteoarthritis pattern 1
• Enlarged joints likely represent bony enlargement (Heberden's nodes at DIPs, Bouchard's nodes at PIPs), not soft tissue swelling 1
• Normal RF is expected in OA 3
• Mildly elevated ESR (15) can occur in OA and does not indicate inflammatory arthritis 4

Why This is NOT Seronegative RA:

• RA predominantly affects MCP and PIP joints while explicitly sparing DIPs 1
• DIP involvement in RA is extremely rare 1
• The joint pattern described (PIP + DIP) contradicts the MCP + PIP pattern characteristic of RA 1

Critical Examination Needed

You must distinguish bony enlargement from soft tissue swelling on physical examination:

• Palpate for hard, bony enlargement (Heberden's/Bouchard's nodes) = osteoarthritis 1
• Soft, boggy swelling = inflammatory arthritis 1
• Morning stiffness >30 minutes suggests inflammatory arthritis; brief stiffness suggests OA 1

Treatment Approach for Hand Osteoarthritis

First-Line Non-Pharmacologic Management:

• Begin with exercise and physical/occupational therapy referral 5
• Hand exercises and joint protection techniques from occupational therapy 5
• Weight management if applicable 5
• Education and self-management programs 5

Pharmacologic Management Algorithm:

Step 1: Start with topical NSAIDs for hand OA 5

• Topical agents are recommended for specific joints in OA 5
• Less systemic exposure than oral NSAIDs 6

Step 2: Add oral acetaminophen (paracetamol) if topical therapy insufficient 5

• Recommended as first-line oral treatment 5

Step 3: Oral NSAIDs if above measures fail 5

• Use lowest effective dose for shortest duration 5
• Assess cardiovascular, gastrointestinal, and renal risk before prescribing 5

Step 4: Consider intra-articular corticosteroid injections for specific severely affected joints 5

Multimodal Approach:

Combine physical and pharmacologic interventions rather than relying on single medication 5

• Physical therapy + topical NSAIDs + acetaminophen as needed 5
• Thermal therapies (heat/cold) 5
• Splinting for specific joints if indicated 5

Common Pitfall to Avoid

Do not treat this as seronegative RA with DMARDs based solely on elevated ESR. 4 Normal ESR, CRP, and RF are seen in 15% of actual RA patients, but more importantly, the DIP involvement pattern here definitively points to OA, not RA. 1, 4 Approximately 35-45% of RA patients have normal inflammatory markers at presentation, but they still have the characteristic MCP/PIP pattern without DIP involvement. 4

If any doubt remains, obtain hand radiographs looking for:

• Osteophytes and joint space narrowing at DIPs/PIPs = OA 1
• Periarticular erosions at MCPs/PIPs with DIP sparing = RA 1

When to Reconsider the Diagnosis

Refer to rheumatology if:

• Soft tissue swelling (not bony) is confirmed on examination 1
• Morning stiffness exceeds 30-60 minutes 1
• MCP joints become involved 1
• Anti-CCP antibodies are positive (should be checked if clinical suspicion for RA persists) 5, 3
• Symptoms progress despite appropriate OA management 5