What is the best course of treatment for a patient presenting with unilateral Proximal Interphalangeal (PIP) joint swelling and painless rough skin, suggestive of psoriatic arthritis?

Unilateral PIP Joint Swelling with Painless Rough Skin: Diagnostic and Treatment Approach

This presentation strongly suggests psoriatic arthritis (PsA), and you should initiate treatment with methotrexate 15-25 mg weekly plus folic acid supplementation while arranging rheumatology consultation for confirmation and co-management. 1, 2

Critical Diagnostic Features to Confirm

The unilateral PIP joint swelling with rough skin is highly characteristic of PsA, particularly when considering:

• Nail involvement - Look specifically for nail pitting, onycholysis, or dystrophy, which occurs in 80-90% of PsA patients and is especially common with distal interphalangeal (DIP) joint involvement 1
• Dactylitis - Examine for "sausage digit" appearance of the entire affected finger, which represents a combination of enthesitis and synovitis 1
• Enthesitis - Palpate for tenderness at tendon insertion sites including lateral epicondyle, medial femoral condyle, and Achilles tendon insertion 1, 3
• Morning stiffness - Ask specifically about early morning stiffness lasting >30 minutes, which is a valuable screening question 1
• Psoriatic skin lesions - The "rough skin" may represent psoriatic plaques; examine scalp, elbows, knees, and gluteal cleft for additional lesions 1

When to Refer to Rheumatology

Refer immediately if you are uncertain of the diagnosis or if the patient has classic signs (swollen/tender joints, prolonged morning stiffness) unresponsive to NSAIDs. 1 The rheumatologist will perform comprehensive joint assessment, obtain radiographs, and measure inflammatory markers (ESR, CRP) 1

Initial Treatment Algorithm

For Mild Disease (Oligoarticular, <5 joints involved)

• Start NSAIDs as first-line therapy for symptom control 1, 2
• Add intra-articular corticosteroid injection for the affected PIP joint if inflammation persists after 2-3 months of NSAID therapy 1, 2
• Avoid injecting through psoriatic plaques when performing local corticosteroid injections 2

For Moderate to Severe Disease (≥5 swollen joints, elevated ESR/CRP, or structural damage)

Initiate methotrexate 15-25 mg weekly with folic acid 1 mg daily immediately, without waiting for confirmatory testing. 1, 2 This is the preferred initial DMARD when significant skin involvement coexists with peripheral arthritis 2

• Methotrexate has Level A evidence for treating both moderate-to-severe psoriasis and peripheral arthritis 2
• The combination addresses both skin and joint manifestations simultaneously 1, 4
• If unresponsive after 2-3 months of methotrexate, escalate to TNF inhibitor therapy 1

Poor Prognostic Factors Requiring Aggressive Treatment

Consider starting TNF inhibitors earlier (even without failing methotrexate) if any of the following are present: 1, 2

• Polyarticular disease (≥5 joints)
• Elevated inflammatory markers (ESR/CRP) attributable to PsA
• Existing structural damage or erosions on radiographs
• Rapidly progressive disease
• Severe functional impairment

TNF Inhibitor Selection When Indicated

For patients requiring biologic therapy, TNF inhibitors are first-line with the following options having Level A evidence: 1, 2

• Adalimumab 40 mg subcutaneously every other week 5
• Etanercept 50 mg subcutaneously weekly or 25 mg twice weekly 6
• Infliximab (requires infusion) 1

All three TNF inhibitors are equally effective for peripheral arthritis and inhibit radiographic progression 2. They can be used as monotherapy or combined with methotrexate at reduced doses (10-15 mg weekly) 2

Critical Pitfalls to Avoid

• Do not delay treatment waiting for serology - There is no specific serologic test to definitively diagnose PsA in the United States 1
• Do not assume mild skin disease means mild joint disease - The severity of skin and joint manifestations do not correlate 1
• Do not use systemic corticosteroids liberally - While low-dose systemic steroids (≤7.5 mg/day) may be used cautiously, skin flares can occur upon withdrawal 1
• Do not ignore the 20% who develop arthritis before skin changes - PsA can precede psoriasis, sometimes by many years 1, 7

Baseline Monitoring Before Starting Methotrexate

Obtain the following before initiating therapy 8:

• Complete blood count
• Comprehensive metabolic panel (liver and kidney function)
• Hepatitis B and C screening
• Chest X-ray
• Pregnancy test (if applicable)

Long-Term Prognosis Considerations

Left untreated, 40-60% of PsA patients develop erosive and deforming arthritis, which may progress within the first year. 1 Patients with PsA have approximately 60% higher risk of premature mortality than the general population, with life expectancy shortened by approximately 3 years 7. Early aggressive treatment substantially improves long-term prognosis 7