What is the diagnosis and treatment for a 61-year-old female with chronic inflammatory arthritis, presenting with foot pain, plantar pain, bilateral ankle and toe deformities, nail dystrophy, and elevated Erythrocyte Sedimentation Rate (ESR) and Rheumatoid Factor (RF)?

Diagnosis: Seronegative Rheumatoid Arthritis

This patient has seronegative rheumatoid arthritis (RA), not psoriatic arthritis, and should be started immediately on methotrexate without waiting for anti-CCP or HLA-B27 results. 1

Clinical Reasoning

Why Rheumatoid Arthritis is the Diagnosis

The clinical presentation strongly supports RA based on the 2010 ACR/EULAR classification criteria, which requires ≥6/10 points 1:

• Joint involvement (5 points): Bilateral symmetric polyarticular disease affecting small joints (MCPs, PIPs, DIPs, MTPs) with characteristic deformities (swan neck, ulnar deviation, claw toes) 1
• Serology (0 points): RF negative (6.4 IU/mL is normal), anti-CCP pending but likely negative given RF negativity 1
• Acute phase reactants (1 point): ESR 17 mm/hr is mildly elevated, hsCRP 0.52 mg/dL is elevated 1
• Duration (1 point): Symptoms progressive over 3-4 years, clearly >6 weeks 1

Total score: 7 points, meeting diagnostic threshold for definite RA 1

Why This is NOT Psoriatic Arthritis

The absence of psoriatic features is critical 2:

• No skin psoriasis: No plaques, pustules, or active skin lesions anywhere on body 2, 3
• No characteristic nail changes: The nail dystrophy described (thickened, irregular second toe nail) is non-specific; there is no oil-drop discoloration, no pitting, which are hallmarks of psoriatic nail disease 2, 3
• No dactylitis: Despite careful examination, no "sausage digits" are documented 2, 3
• No enthesitis: No documented Achilles tendon involvement or other entheseal inflammation 2, 3
• Pattern of joint involvement: The bilateral symmetric polyarthritis with swan neck deformities and ulnar deviation is classic for RA, not the asymmetric oligoarthritis or DIP-predominant pattern typical of early PsA 3, 4

Poor Prognostic Indicators Present

This patient has multiple factors predicting aggressive disease and joint damage 2, 1:

• Polyarticular disease: Multiple joints involved bilaterally 2
• Established deformities: Swan neck, ulnar deviation, claw toes indicate structural damage already present 2, 1
• Elevated ESR: Even mild elevation (17 mm/hr) is associated with worse outcomes 2, 5
• Progressive course: Worsening over 3-4 years indicates active, untreated inflammatory disease 1, 4

Treatment Recommendations

Immediate Management

Start methotrexate 15-20 mg weekly with folic acid 1 mg daily immediately, without waiting for anti-CCP or HLA-B27 results 1:

• The clinical diagnosis is clear based on ACR/EULAR criteria (score of 7) 1
• Serology does not change the diagnosis when clinical criteria are met 1
• Delaying treatment risks further irreversible joint damage 1, 4
• Methotrexate is first-line DMARD therapy for RA 1, 6

Symptomatic Control

Add NSAIDs (naproxen 500 mg twice daily or celecoxib 200 mg daily) for pain control 2:

• Monitor for gastrointestinal and renal side effects 1
• Consider gastroprotection with proton pump inhibitor given chronic use 2

Consider short-term low-dose prednisone (5-10 mg daily) as bridge therapy for 4-8 weeks 2, 1:

• Provides rapid symptom relief while awaiting DMARD effect 2
• Taper and discontinue once methotrexate takes effect (typically 6-12 weeks) 2, 1
• Avoid chronic systemic corticosteroid use due to adverse effects 2, 7

Monitoring and Follow-Up

Baseline assessments before starting methotrexate 2, 1:

• Complete blood count, comprehensive metabolic panel (already done, normal)
• Hepatitis B and C screening
• Chest X-ray to exclude latent tuberculosis
• Pregnancy test if applicable

Regular monitoring on methotrexate 1, 6:

• CBC, liver function tests, creatinine every 4-8 weeks initially, then every 8-12 weeks when stable 6
• Clinical assessment of disease activity every 3 months 2, 1
• Target DAS28 <2.6 (remission) or <3.2 (low disease activity) 1

Obtain baseline hand/wrist and foot radiographs 2, 1:

• Document existing structural damage 2
• Repeat annually to assess progression 2, 1

Escalation Strategy if Inadequate Response

If inadequate response to methotrexate after 3-6 months (persistent swollen/tender joints, elevated ESR/CRP, or radiographic progression) 2:

• Switch to TNF inhibitor biologic (adalimumab, etanercept, infliximab, golimumab, or certolizumab) 2
• Continue methotrexate in combination with TNF inhibitor for synergistic effect 2, 4
• Alternative: Switch to different oral DMARD (leflunomide 20 mg daily) if contraindications to biologics exist 2, 6

Common Pitfalls to Avoid

Do not wait for serology to start treatment 1:

• 20-30% of RA patients are seronegative for both RF and anti-CCP 1
• Clinical criteria alone are sufficient for diagnosis when score ≥6 1
• Treatment delay leads to irreversible joint damage 1, 4

Do not misdiagnose as psoriatic arthritis without skin findings 2, 3:

• While PsA can rarely precede skin psoriasis, the symmetric polyarticular pattern with characteristic RA deformities makes this diagnosis unlikely 3, 8
• The nail changes described are non-specific and lack the oil-drop sign or pitting characteristic of psoriatic nail disease 2, 3

Do not use chronic systemic corticosteroids 2, 7:

• Only use as short-term bridge therapy 2, 1
• Chronic use causes significant adverse effects without disease-modifying benefit 2, 7

Do not underestimate disease severity 2, 1:

• Established deformities indicate this is not "mild" disease 2, 1
• Aggressive DMARD therapy is warranted, with low threshold for biologic escalation 2