What is the likely diagnosis and management for a patient with bilateral hand pain and swelling, and an elevated C-Reactive Protein (CRP) level of 34?

Bilateral Hand Pain and Swelling with CRP 34: Diagnosis and Management

Most Likely Diagnosis

The most likely diagnosis is rheumatoid arthritis (RA), given the bilateral hand involvement and elevated inflammatory markers, though erosive hand osteoarthritis and psoriatic arthritis must be excluded. 1, 2

Diagnostic Approach

Immediate Clinical Assessment

Examine specific joint patterns to differentiate between conditions:

• For RA: Look for symmetric involvement of MCPJs and PIPJs, sparing DIPJs, with morning stiffness >45 minutes and soft tissue swelling 1, 3, 4
• For erosive osteoarthritis: Check for Heberden nodes (DIPJs) and Bouchard nodes (PIPJs), with abrupt onset pain, soft tissue swelling, and erythema—this condition characteristically shows mildly elevated CRP 1
• For psoriatic arthritis: Search for psoriatic skin lesions, nail pitting, dactylitis (sausage digits), and asymmetric or single-ray involvement, particularly targeting DIPJs 1

Essential Laboratory Testing

Order the following tests immediately to establish diagnosis:

• Rheumatoid factor (RF) and anti-CCP antibodies: Positive serology strongly supports RA diagnosis, though 20-30% of RA patients are seronegative 2, 4, 5
• Complete blood count with differential: Assess for anemia (common in RA) and thrombocytosis (indicates active inflammation) 2, 4
• Comprehensive metabolic panel: Evaluate renal and hepatic function before initiating DMARDs 2, 4
• ESR measurement: CRP of 34 mg/L is significantly elevated; ESR will help confirm systemic inflammation and is incorporated into disease activity scoring 6, 3, 7

Note: A CRP of 34 mg/L is moderately elevated and strongly suggests active inflammatory arthritis rather than mechanical joint disease 6, 7, 8

Imaging Studies

Obtain posteroanterior radiographs of both hands on a single film:

• This is the gold standard for morphological assessment and will differentiate RA (periarticular erosions, joint space narrowing at MCPJs/PIPJs) from erosive OA (subchondral erosions at IPJs with osteophytes) 1
• Radiographs also establish baseline for monitoring disease progression 4, 5

Differential Diagnosis Considerations

Key Distinguishing Features

Rheumatoid Arthritis (Most Likely):

• Bilateral symmetric polyarthritis targeting MCPJs and PIPJs 2, 4, 5
• Prolonged morning stiffness (>45 minutes) 3, 4
• Elevated CRP and ESR are consistent with active disease 3, 5, 7
• Progressive course over months to years 2, 4

Erosive Hand Osteoarthritis (Important Alternative):

• Targets IPJs specifically (DIPJs and PIPJs), sparing MCPJs 1
• Abrupt onset with marked pain and inflammatory signs 1
• Mildly elevated CRP levels are characteristic 1
• Presence of Heberden and Bouchard nodes 1
• Worse functional outcome than non-erosive OA 1

Psoriatic Arthritis:

• May target DIPJs or affect single rays asymmetrically 1
• Look for psoriatic plaques, nail changes, dactylitis 1
• Can have elevated inflammatory markers 1

Gout:

• May superimpose on pre-existing hand OA 1
• Typically more acute, episodic presentation 1

Management Strategy

If Rheumatoid Arthritis is Confirmed

Start methotrexate 15-20 mg weekly with folic acid 1 mg daily immediately, without waiting for serology results if clinical diagnosis is clear: 2, 4, 5

• The 2010 ACR/EULAR criteria require ≥6 points for definite RA diagnosis (points for: joint involvement, serology, acute phase reactants, symptom duration >6 weeks) 2
• Earlier DMARD initiation is associated with better long-term outcomes 4, 5

Add bridging therapy for symptom control:

• Short-term prednisone 5-10 mg daily for 4-8 weeks, then taper as methotrexate takes effect 2
• NSAIDs (naproxen 500 mg twice daily or celecoxib 200 mg daily) with monitoring for GI and renal side effects 2

Baseline monitoring before methotrexate:

• Hepatitis B and C screening, tuberculosis testing, pregnancy test 2, 4
• Chest X-ray 2

If Erosive Hand Osteoarthritis is Diagnosed

The management differs significantly from RA:

• Blood tests are not required for diagnosis but may screen for coexistent inflammatory arthritides given the marked inflammatory symptoms 1
• Treatment focuses on pain management and functional preservation rather than disease-modifying therapy 1
• This subset has worse functional outcomes and requires careful monitoring 1

Treatment Goals and Monitoring

Target remission or low disease activity (DAS28 <2.6 for remission, <3.2 for low disease activity): 2, 3

• Monitor ESR and CRP every 1-3 months during active disease, then every 3-6 months once remission achieved 6, 3
• Assess CBC, liver function, and creatinine regularly on methotrexate 2
• If inadequate response after 3-6 months, add TNF inhibitor biologic (adalimumab, etanercept, infliximab) while continuing methotrexate 2

Critical Pitfalls to Avoid

Do not delay DMARD therapy waiting for positive serology: 20-30% of RA patients are seronegative, and clinical diagnosis with elevated inflammatory markers is sufficient to start treatment 2, 4, 5

Do not dismiss erosive OA as "just arthritis": This subset has inflammatory features, mildly elevated CRP, and significantly worse outcomes than typical OA, requiring different management 1

Do not rely on CRP alone: ESR provides complementary information and is incorporated into validated disease activity measures; obtain both for comprehensive assessment 6, 3

Do not overlook psoriatic arthritis: Carefully examine skin, nails, and assess for dactylitis, as DIPJ involvement can occur in both erosive OA and psoriatic arthritis 1