What is the diagnosis for a 61-year-old female with foot pain, plantar pain, bilateral ankle and toe deformities, and recent onset of hyperkeratosis, with laboratory results showing elevated Rheumatoid Factor (RF) and pending anti-Cyclic Citrullinated Peptide (anti-CCP) and Human Leukocyte Antigen B27 (HLA B27) results?

Diagnosis: Rheumatoid Arthritis (Seronegative)

This patient has rheumatoid arthritis based on the 2010 ACR/EULAR classification criteria, despite a negative rheumatoid factor, as seronegative RA accounts for 20-30% of cases and has similar prognosis to seropositive disease. 1

Clinical Scoring Using 2010 ACR/EULAR Criteria

This patient's presentation yields a score that meets the threshold for definite RA (≥6/10 points required): 2

A) Joint Involvement Score: 5 points

• Multiple small joints affected bilaterally: MCPs (bilateral thumb and little finger tenderness), PIPs (swan neck deformities in ring and little fingers), wrists (bilateral ulnar deviation), and MTPs (2nd toe involvement with hammer toe deformities) 2
• Pattern indicates >10 joints with at least 1 small joint involvement = 5 points 2

B) Serology Score: 0 points

• RF = 6.4 IU/mL (negative, as normal is ≤14-15 IU/mL) 3
• Anti-CCP pending but RF negativity = 0 points 2
• Critical point: Negative RF does NOT exclude RA—20-30% of RA cases are seronegative 1

C) Acute Phase Reactants: 0 points

• ESR = 4 (normal), hsCRP = 0.52 (normal) = 0 points 2
• Important caveat: Normal acute phase reactants do NOT exclude RA, as they are poor predictors and can be normal even in active disease 1

D) Duration of Symptoms: 1 point

• Progressive symptoms over 3-4 years (≥6 weeks) = 1 point 2

Total Score: 6/10 points = Definite Rheumatoid Arthritis 2

Key Clinical Features Supporting RA Diagnosis

Hand Deformities (Classic RA Pattern)

• Ulnar deviation at MCPs bilaterally 2, 1
• Swan neck deformities in bilateral ring and little fingers 2, 1
• Ulnar deviation of bilateral wrists 2, 1
• Interosseous muscle wasting and dorsal hand flattening 2, 1
• Symmetric small joint involvement is characteristic of RA 1

Foot Deformities (RA-Associated)

• Bilateral hammer toe deformities (2nd toes) 2, 1
• Bilateral hindfoot valgus with pes planovalgus 2, 1
• MTP joint involvement (2nd MTPs affected) 2, 1

Predictors of Persistent/Progressive Disease Present

• Female gender (61-year-old woman) 2
• Duration >6 weeks (years in this case) 2
• Small joint involvement 2
• Multiple joint involvement (>3 joints) 2
• Functional impairment (progressive symptoms affecting daily activities) 2

Critical Differential Diagnoses Excluded

Psoriatic Arthritis: Excluded

• No skin plaques, pustules, or nail pitting 1
• No oil-drop nail changes 2
• No dactylitis 2
• Nail dystrophy present is hyperkeratotic, not psoriatic 2

Gout: Excluded

• Normal uric acid level 1
• Chronic progressive polyarticular pattern (not episodic monoarticular) 1

Spondyloarthropathy: Excluded

• HLA-B27 pending, but no axial/entheseal involvement documented 2
• Pattern is symmetric polyarthritis, not oligoarticular 2

Immediate Next Steps Required

1. Confirm Anti-CCP Status (Pending)

• Anti-CCP has 95% specificity and 60% sensitivity for RA 2, 4
• If positive, increases diagnostic certainty and indicates worse prognosis 2
• If negative, does NOT change diagnosis—seronegative RA is established 1

2. Obtain Baseline Imaging Immediately

• Bilateral hand, wrist, and foot X-rays are essential for detecting erosions and monitoring structural damage progression 2, 1
• Erosions predict RA diagnosis and disease persistence 2, 1
• Repeat X-rays within 1 year to assess progression 2

3. Initiate Disease-Modifying Therapy Without Delay

• Methotrexate is first-line DMARD for RA 1, 5
• DO NOT delay treatment waiting for positive serology—seronegative RA has similar prognosis and requires immediate treatment 1
• Target remission (SDAI ≤3.3) or low disease activity (SDAI ≤11) 1
• Screen for hepatitis B, hepatitis C, and tuberculosis before starting therapy 1, 5

4. Establish Disease Activity Monitoring

• Use DAS28, SDAI, or CDAI for serial assessments 2, 1
• Reassess every 3 months; if inadequate response, add triple DMARD therapy or biologic agent (TNF inhibitor) 1

Common Pitfalls to Avoid

Do not dismiss RA diagnosis based on:

• Negative RF (present in 20-30% of RA cases) 1
• Normal ESR/CRP (poor predictors, can be normal in active disease) 1
• Absence of rheumatoid nodules (not required for diagnosis) 2

Do not delay treatment:

• Early aggressive therapy with DMARDs improves long-term outcomes, prevents joint destruction, and preserves work capacity 2, 5
• 80% of patients are working at 2 years, only 68% at 5 years without early treatment 2