What is the diagnosis and treatment plan for a 61-year-old female patient with foot pain, plantar pain, bilateral ankle and toe deformities, hyperkeratosis, and chronic low backache, with laboratory results showing elevated Rheumatoid Factor (RF) and pending anti-CCP and HLA B27 results?

Diagnosis: Seronegative Rheumatoid Arthritis

This patient has seronegative rheumatoid arthritis (RA) based on the characteristic symmetric polyarticular deformities (ulnar deviation, swan neck deformities, hammer toes), muscle wasting, and chronic progressive course, despite a low RF of 6.4 IU/mL. 1

Clinical Features Supporting RA Diagnosis

The patient meets multiple diagnostic criteria for RA under the 2010 ACR/EULAR classification system, which requires ≥6/10 points:

• Joint involvement (5 points): Bilateral involvement of >10 joints including small joints (MCPs, wrists, toes) 1
• Duration >6 weeks (1 point): Progressive symptoms over 3-4 years 1
• Functional impairment: Chronic pain affecting daily activities is a predictor of persistent/progressive disease 1

The RF of 6.4 IU/mL is negative (normal <14 IU/mL typically), but this does NOT exclude RA—20-30% of RA cases are seronegative with similar prognosis to seropositive disease. 1, 2 The normal ESR (4) and low hsCRP (0.52) also do not exclude RA, as 40% of RA patients have normal acute phase reactants. 2

Key Diagnostic Deformities

The hand and foot deformities are pathognomonic for RA:

• Ulnar deviation at MCPs bilaterally with swan neck deformities (ring and little fingers) 3
• Interosseous, thenar, and hypothenar muscle wasting indicating chronic disease 3
• Hammer toes with medial deviation and crowding—characteristic of RA foot involvement 3
• Symmetric distribution affecting metacarpophalangeal, wrist, and metatarsophalangeal joints 3

The absence of psoriatic features (no plaques, no oil drop changes, no pitting, no dactylitis) and absence of axial/entheseal features (no Achilles tendon tenderness) argues strongly against psoriatic arthritis or spondyloarthropathy. 4

Critical Next Steps

1. Confirm Anti-CCP Status (URGENT)

Anti-CCP testing is essential and must be obtained immediately. 1 Anti-CCP has 95% specificity and 60% sensitivity for RA, and a positive result would confirm the diagnosis even with negative RF. 1 Approximately 5-10% of patients are RF-negative but anti-CCP-positive. 5

2. Obtain Baseline Imaging

Order bilateral hand, wrist, and foot X-rays immediately to assess for erosions. 4, 1 The presence of erosions is highly predictive of RA and indicates more aggressive disease requiring immediate treatment. 4 Given the chronic deformities present, erosions are likely already established. 1

3. Initiate DMARD Therapy Without Delay

Start methotrexate 15-25 mg weekly immediately—do NOT wait for anti-CCP results given the obvious clinical deformities and chronic progressive course. 6, 5 Early aggressive therapy with DMARDs improves long-term outcomes and prevents further joint destruction. 1, 6

Add prednisone 10-15 mg daily as bridging therapy for rapid symptom control while methotrexate takes effect (typically 6-12 weeks). 6

4. Establish Disease Activity Monitoring

Use validated composite measures for serial assessments:

• DAS28, SDAI, or CDAI should be calculated at baseline and every 3 months 6, 7
• Target remission (SDAI ≤3.3) or low disease activity (SDAI ≤11) 6

HLA-B27 Interpretation

The pending HLA-B27 test is unlikely to change management. HLA-B27 is useful when spondyloarthritis is suspected (inflammatory back pain, sacroiliitis, asymmetric arthritis, enthesitis). 4 This patient has:

• Symmetric polyarthritis (not asymmetric) 3
• No inflammatory back pain features
• No enthesitis (negative Achilles tendon examination) 4
• Chronic low back pain is likely mechanical given age and chronic disease

HLA-B27 positivity occurs in only 7-15% of isolated sacroiliitis with IBD and has lower prevalence in RA than idiopathic AS, making it unreliable as a diagnostic test here. 4

Common Pitfalls to Avoid

• Do NOT dismiss RA diagnosis based on negative RF, normal ESR/CRP, or absence of rheumatoid nodules—these do not exclude the diagnosis. 1, 2
• Do NOT delay treatment waiting for anti-CCP results—the clinical picture is diagnostic, and early aggressive therapy is critical. 1, 6
• Do NOT attribute symptoms to osteoarthritis based on age—the symmetric distribution, muscle wasting, and specific deformity patterns are inconsistent with OA. 4

Prognosis and Monitoring

Without aggressive treatment, expect continued joint destruction, work disability (>30% of RA patients), and reduced life expectancy by 3-5 years. 6 However, early aggressive treatment targeting remission dramatically improves outcomes. 6

Monitor for extra-articular manifestations including interstitial lung disease, vasculitis, and inflammatory eye disease, particularly if anti-CCP is positive. 6 The nail dystrophy noted may represent chronic trauma from deformities rather than a specific extra-articular manifestation.