Diagnosing Body Pain Associated with Psoriasis
Body pain associated with psoriasis should be evaluated for psoriatic arthritis (PsA) through a thorough history, physical examination, and when necessary, laboratory tests and imaging, as PsA affects approximately 30% of psoriasis patients and can lead to permanent joint damage if left untreated. 1
Clinical Presentation of Psoriasis-Related Pain
Psoriasis-related pain can manifest in several distinct patterns:
Psoriatic Arthritis (PsA)
Joint symptoms:
- Inflammatory joint pain (different from osteoarthritis)
- Morning stiffness lasting >30 minutes
- Joint swelling and tenderness
- Dactylitis ("sausage digits") - swelling of entire fingers or toes
- Enthesitis - inflammation at tendon/ligament insertion sites 1
Distribution patterns:
Skin Pain
- Direct pain from skin lesions - particularly in areas with cracks, fissures, or pustules
- Pain from skin sensitivity to everyday stimuli
- Pain from excessive scratching due to itch (a common co-symptom) 2
Diagnostic Approach
1. Clinical History
Look specifically for:
- Joint pain with inflammatory characteristics (worse with rest, improves with activity)
- Morning stiffness lasting >30 minutes
- Joint swelling episodes
- Family history of psoriasis or PsA
- Temporal relationship between skin and joint symptoms (skin lesions precede joint symptoms in ~73% of cases) 1
2. Physical Examination
Focus on:
- Joint assessment: Look for tenderness, swelling, redness, warmth
- Enthesitis sites: Achilles tendon, plantar fascia insertion, lateral epicondyles
- Dactylitis: Sausage-shaped digits
- Skin examination: Document psoriatic lesions
- Nail changes: Pitting, onycholysis, hyperkeratosis (strong association with PsA)
3. Laboratory Testing
- Rheumatoid factor (typically negative in PsA)
- C-reactive protein (may be elevated)
- Erythrocyte sedimentation rate
- HLA-B27 (especially in axial disease)
4. Imaging
- X-rays of affected joints (may show erosions, joint space narrowing)
- Ultrasound with power Doppler (can detect subclinical enthesitis)
- MRI (for axial involvement or when diagnosis is uncertain) 1
Distinguishing Features from Other Pain Conditions
- Vs. Rheumatoid Arthritis: PsA typically has asymmetric joint involvement, DIP involvement, dactylitis, enthesitis, negative rheumatoid factor, and nail changes
- Vs. Osteoarthritis: PsA has inflammatory features (morning stiffness >30 min), enthesitis, dactylitis
- Vs. Fibromyalgia: PsA has objective joint swelling, enthesitis on imaging, response to anti-inflammatory therapy
Screening Tools
Several screening tools exist for PsA in psoriasis patients:
- Psoriasis Epidemiology Screening Tool (PEST)
- Toronto Psoriatic Arthritis Screen (ToPAS)
- Psoriatic Arthritis Screening and Evaluation (PASE)
- Early Arthritis for Psoriatic Patients (EARP)
However, these tools have limitations and may not perform consistently across different populations 1.
When to Refer to a Specialist
Referral to a rheumatologist is recommended when:
- Signs and symptoms of inflammatory arthritis are present
- Diagnosis is uncertain
- Pain persists despite initial treatment
- There is evidence of joint damage or functional impairment 1
Additionally, patients with PsA should be screened for uveitis with referral to ophthalmology if eye symptoms develop 1.
Important Considerations
Early diagnosis is critical: Up to 50% of untreated PsA patients may develop permanent joint damage 1
PsA can precede skin disease: In 14.9-19.4% of cases, joint symptoms appear before skin manifestations 1
Comorbidity screening: Patients with psoriasis and PsA have increased risk of cardiovascular disease, diabetes, and metabolic syndrome 1
Pain impact: Psoriasis-related pain significantly impacts quality of life, physical activity, sleep, and emotional well-being 2
By following this systematic approach, clinicians can effectively diagnose body pain associated with psoriasis and initiate appropriate treatment to prevent long-term joint damage and disability.