Summary

Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy associated with psoriasis. It belongs to the spondyloarthritis (SpA) family and can affect peripheral joints, the axial skeleton, entheses, and skin/nails. Clinical patterns include distal interphalangeal (DIP) predominant, asymmetric oligoarticular, symmetric polyarticular (RA-like), axial, and arthritis mutilans. The CASPAR criteria are used for classification. Unlike rheumatoid arthritis, PsA is typically rheumatoid factor negative and associated with HLA-B27 (especially axial disease). Treatment follows a treat-to-target approach with NSAIDs, conventional DMARDs (methotrexate), and biologics (TNF inhibitors, IL-17 inhibitors, IL-23 inhibitors).

Key Facts

• Definition: Inflammatory arthritis associated with psoriasis
• Incidence: Affects 20-30% of psoriasis patients; overall prevalence 0.1-0.25%
• Demographics: Equal sex distribution; onset typically 30-50 years
• Pathognomonic: Psoriasis + dactylitis + DIP involvement + nail dystrophy + RF negative
• Gold Standard Investigation: Clinical diagnosis + imaging (X-ray, MRI, ultrasound)
• First-line Treatment: NSAIDs for symptoms; MTX for peripheral; biologics for inadequate response
• Prognosis: Variable; early aggressive treatment prevents joint damage

Clinical Pearls

Dactylitis Pearl: "Sausage digit" (dactylitis) is highly specific for PsA/SpA. Involves entire digit due to flexor tenosynovitis + synovitis.

Nail Pearl: Nail pitting, onycholysis, and hyperkeratosis correlate with DIP arthritis and predict more severe disease.

RF Pearl: PsA is typically RF and anti-CCP negative. Positive RF should prompt consideration of coexistent RA.

Skin-Joint Link Pearl: Skin psoriasis precedes arthritis in 70-80% of cases by an average of 10 years.

Axial Pearl: Axial PsA is often asymmetric (unlike AS) and may have bulky, asymmetric syndesmophytes.

Why This Matters Clinically

PsA causes progressive joint damage if untreated. Early recognition and treat-to-target strategies with biologics dramatically improve outcomes. All psoriasis patients should be screened regularly for joint symptoms.

Skin Examination

• Psoriatic plaques (hidden sites: scalp, ears, umbilicus, natal cleft)
• Nail examination: pitting, onycholysis, hyperkeratosis, oil spots
• Assess psoriasis severity (PASI score)

Joint Examination

Hands:

• DIP swelling and tenderness
• Dactylitis (sausage digits)
• Nail changes adjacent to affected DIPs
• Deformity (mutilans pattern)

Feet:

• MTP involvement
• Dactylitis
• Heel pain (enthesitis)

Spine:

• Lumbar spine mobility (Schober's test)
• Chest expansion
• Cervical rotation

Enthesis Examination

• Achilles tendon insertion
• Plantar fascia (heel)
• Lateral epicondyles
• Anterior tibial tuberosity
• Iliac crest

MASES Score (Maastricht Ankylosing Spondylitis Enthesitis Score)

13 entheseal sites examined for tenderness.

Natural History

• Persistent inflammation in 60-70%
• Erosive disease in 40-60% within 2 years if untreated
• Better outcomes with early aggressive treatment

Prognostic Factors

Poor prognosis:

• Polyarticular disease at onset
• Elevated inflammatory markers
• Prior joint damage
• Dactylitis
• Nail disease
• Delay in treatment

Disease Activity Measures

• DAPSA (Disease Activity in Psoriatic Arthritis)
• MDA (Minimal Disease Activity) - target
• PASDAS (Psoriatic Arthritis Disease Activity Score)

Key Guidelines

1. GRAPPA 2021 Treatment Recommendations — Coates LC et al. Nat Rev Rheumatol. 2022;18(8):465-479.

2. EULAR 2019 Recommendations for PsA — Gossec L et al. Ann Rheum Dis. 2020;79(6):700-712. PMID: 32434812

3. ACR/NPF 2018 Guideline — Singh JA et al. Arthritis Rheumatol. 2019;71(1):5-32. PMID: 30499246

Landmark Trials

DISCOVER-1 and DISCOVER-2 (Guselkumab)

• IL-23 inhibitor efficacy in PsA
• ACR20 response 59-64% vs placebo 22%
• PMID: 31986068

SPIRIT-P1 (Ixekizumab)

• IL-17A inhibitor in biologic-naive PsA
• ACR20 response 58% vs placebo 30%
• PMID: 28160507

SELECT-PsA (Upadacitinib)

• JAK inhibitor efficacy
• ACR20 response 71% vs placebo 36%
• PMID: 33125870

What is Psoriatic Arthritis?

Psoriatic arthritis is a type of inflammatory arthritis that occurs in some people with psoriasis. It causes pain, swelling, and stiffness in your joints. It can also affect your tendons and spine.

How is it different from other types of arthritis?

Unlike rheumatoid arthritis, PsA often affects the distal finger joints (near the nails) and can cause "sausage fingers." It's also associated with skin and nail changes from psoriasis.

Treatment

We aim to control inflammation early to prevent joint damage. Treatments include anti-inflammatory medications, disease-modifying drugs like methotrexate, and newer biological therapies that target specific parts of your immune system.

What can I do?

• Stay active with regular, gentle exercise
• Maintain a healthy weight
• Don't smoke
• Take your medications as prescribed
• Tell your doctor about any new symptoms

Viva Points

"PsA is an inflammatory arthropathy in the SpA family, associated with psoriasis. CASPAR criteria: psoriasis + dactylitis + nail changes + RF negative + juxta-articular new bone. Treatment follows domains: NSAIDs for all, MTX for peripheral (NOT axial), biologics (TNFi, IL-17i, IL-23i) for inadequate response. Axial disease goes straight to biologics."

Key Examination Points

• Look for hidden psoriasis (scalp, ears, umbilicus, natal cleft)
• Examine nails for pitting, onycholysis
• Assess for dactylitis ("sausage" digits)
• Examine DIPs (unusual in RA)
• Check entheses (Achilles, plantar fascia)
• Spine examination for axial involvement

Common Mistakes

• ❌ Missing hidden psoriasis (scalp, ears, natal cleft)
• ❌ Using MTX for axial disease (doesn't work)
• ❌ Confusing with gout (uric acid may be elevated in psoriasis)
• ❌ Not screening psoriasis patients for joint symptoms

Last Reviewed: 2026-01-01 | MedVellum Editorial Team