What is the most likely rheumatological disease in a patient with polyarthralgia affecting distal and proximal interphalangeal joints, non-tender hard nodules over distal interphalangeal joints, mildly elevated Erythrocyte Sedimentation Rate (ESR) and White Blood Cell (WBC) count, and normal Rheumatoid Factor (RF)?

Hand Osteoarthritis

The most likely diagnosis is hand osteoarthritis (Option B), specifically affecting the distal and proximal interphalangeal joints, as evidenced by the characteristic non-tender hard nodules (Heberden nodes) over the DIP joints, chronic polyarthralgia without significant morning stiffness, absence of active synovitis, and normal inflammatory markers. 1

Key Diagnostic Features Supporting Hand Osteoarthritis

Clinical Presentation

• Non-tender hard nodules over DIP joints are pathognomonic for Heberden nodes, which are clinical hallmarks of hand osteoarthritis and associate strongly with underlying structural changes, particularly osteophyte formation 1
• The involvement of both DIP and PIP joints bilaterally is the classic distribution pattern for hand osteoarthritis, with DIP joints being the most frequently affected site 1
• Absence of significant early morning stiffness (a key distinguishing feature from rheumatoid arthritis, which typically presents with morning stiffness lasting ≥1 hour) 1
• No active arthritis on examination rules out inflammatory arthropathies 1

Laboratory Findings

• Normal rheumatoid factor (30 kIU/L, reference <58 kIU/L) effectively excludes seropositive rheumatoid arthritis 1
• ESR of 15 mm/h is within normal range for females (3-15 mm/h), and the mildly elevated WBC (11 × 10⁹/L) is not clinically significant for inflammatory arthritis 1
• Normal CRP (5 mg/L, reference <8.2 mg/L) argues strongly against active inflammatory arthritis 1
• Blood tests are not required for diagnosis of hand osteoarthritis but help exclude coexistent inflammatory disease 1

Why Other Diagnoses Are Excluded

Seronegative Rheumatoid Arthritis (Option A) - Unlikely

• Rheumatoid arthritis typically targets MCP joints, PIP joints, and wrists rather than DIP joints 1
• Significant early morning stiffness lasting ≥1 hour is a cardinal feature of RA, which this patient lacks 1
• Active synovitis with joint swelling would be expected on examination in untreated RA 1
• The 3-year duration without progression to active inflammatory arthritis makes RA highly improbable 1

Polyarticular Gout (Option C) - Unlikely

• Gout typically presents with acute, episodic attacks of severe pain with erythema and swelling, not chronic polyarthralgia 1
• Hard nodules in gout would be tophi, which are typically tender and may ulcerate, unlike the non-tender nodules described 1
• Normal uric acid levels would be expected to be documented if gout were suspected (not provided in labs)
• The bilateral symmetric DIP involvement is atypical for gout 1

Reactive Arthritis (Option D) - Unlikely

• Reactive arthritis typically presents as acute oligoarthritis (affecting <5 joints) following genitourinary or gastrointestinal infection 1
• Large weight-bearing joints (knees, ankles) are predominantly affected in reactive arthritis, not small hand joints 1
• The 3-year chronic course without preceding infection is incompatible with reactive arthritis 1
• Absence of extra-articular manifestations (conjunctivitis, urethritis) further excludes this diagnosis 1

Clinical Pearls and Diagnostic Considerations

Recognized Subsets of Hand Osteoarthritis

• Erosive hand osteoarthritis is a subset that targets IPJs with radiographic subchondral erosion, typically presenting with abrupt onset, marked pain, inflammatory symptoms (stiffness, soft tissue swelling), and mildly elevated CRP 1
• This patient's presentation is more consistent with non-erosive IPJ osteoarthritis given the chronic course, absence of inflammatory signs, and normal CRP 1

Differential Diagnosis Pitfalls

• Psoriatic arthritis may target DIP joints and should be considered, but typically affects just one ray and would show active inflammation 1
• Gout may superimpose on pre-existing hand osteoarthritis, creating diagnostic confusion, but the chronic non-inflammatory presentation argues against this 1

Recommended Next Steps

• Plain radiographs of both hands (posteroanterior view) provide the gold standard for morphological assessment, showing characteristic features of joint space narrowing, osteophytes, subchondral sclerosis, and subchondral cysts 1
• Functional assessment using validated outcome measures is important, as functional impairment in hand osteoarthritis may be as severe as in rheumatoid arthritis 1
• Patients with polyarticular hand osteoarthritis are at increased risk for knee, hip, and generalized osteoarthritis and should be assessed accordingly 1

Management Approach

• Evaluation by occupational or physical therapist for activities of daily living, joint protection techniques, and thermal modalities 1
• Topical or oral NSAIDs for symptomatic relief (though evidence is limited for hand osteoarthritis) 1
• Assistive devices as needed to maintain function 1