Psoriatic arthritis
Psoriatic arthritis (PsA) is a seronegative spondyloarthritis that develops in up to 30% of patients with psoriasis, producing asymmetric oligoarthritis or distal interphalangeal joint disease, dactylitis, enthesitis, nail dystrophy, and axial involvement. Diagnosis is clinical, supported by the CASPAR criteria. Limited peripheral disease is treated with an NSAID or intra-articular glucocorticoid, more active disease with methotrexate, a tumor necrosis factor inhibitor, or an interleukin-17 inhibitor.
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What this article covers
- Overview
Definition: psoriatic arthritis (PsA) is a seronegative spondyloarthritis occurring in patients with psoriasis or a strong predisposition to it.
- Epidemiology
Psoriasis burden: psoriasis affects approximately 3% of the population, and up to 30% of patients with psoriasis develop psoriatic arthritis.
- Risk factors
Psoriasis severity and site: severe psoriasis and involvement of the scalp, genitals, or intertriginous (inverse) areas.
- Pathophysiology
Entheseal-first inflammation: psoriatic arthritis targets the enthesis, the fibrocartilage-rich site where tendons and ligaments insert into bone, producing enthesitis, dactylitis, and, when the…
- Clinical features
Five overlapping clinical subtypes: asymmetric oligoarthritis of four or fewer, typically large, joints; polyarticular hand disease resembling rheumatoid arthritis; a DIP-predominant pattern…
- Differential diagnosis
Rheumatoid arthritis: symmetric polyarthritis of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints that spares the DIP joints, with a positive rheumatoid factor or anti-cyclic…
- Diagnosis
Diagnosis is clinical, made in a patient with an inflammatory joint pattern plus psoriasis, and supported by the Classification Criteria for Psoriatic Arthritis (CASPAR): current psoriasis (2 points)…
- Management
First, for limited peripheral disease (a single digit with dactylitis or one swollen joint), use an NSAID or an intra-articular glucocorticoid; avoid high-dose oral glucocorticoids, since tapering…
- Complications
Arthritis mutilans: the most destructive subtype, with substantial joint destruction and telescoping digits.
- Prognosis
Course varies by subtype: oligoarticular disease is typically milder, while DIP-predominant and polyarticular disease carry more risk of progression to arthritis mutilans.
- Prevention
Screen every psoriasis patient for joint disease, particularly with nail involvement, at diagnosis and follow-up.
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Psoriasis is a chronic, relapsing, immune-mediated dermatosis of accelerated keratinocyte turnover, classically presenting as sharply demarcated, silvery-scaled plaques on extensor surfaces, with guttate, inverse, pustular, and erythrodermic variants and an associated psoriatic arthritis. Mild-to-moderate disease is treated with emollients and topical corticosteroids with or without a vitamin-D analogue (calcipotriene 0.005% twice daily), while widespread (over 10% body surface area), recalcitrant, or severe disease escalates to phototherapy, methotrexate (weekly single dose 7.5 to 25 mg), or a biologic such as adalimumab, ustekinumab, or secukinumab, never a systemic glucocorticoid.
- Rheumatoid arthritis
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- Gout
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