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Psoriatic Arthritis

GMJ News knowledge hub · last reviewed August 2026 · Georgian Medical Journal

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Psoriatic arthritis (PsA) — a seronegative inflammatory arthritis occurring in approximately 20-30% of people with psoriasis (though it may precede skin disease in up to 15% of cases) — is clinically distinguished from other inflammatory arthritides by its characteristic triad of dactylitis (“sausage digits” — diffuse inflammatory swelling of entire fingers or toes), enthesitis (inflammation at tendon and ligament insertions, particularly Achilles and plantar fascia) and nail involvement (pitting, onycholysis, oil-drop discolouration — present in approximately 80%), together with inflammatory joint disease and a negative rheumatoid factor (WHO). Modern treatment options have expanded dramatically: anti-TNF biologics (adalimumab, etanercept) remain widely used; IL-17A inhibitors (secukinumab, ixekizumab) demonstrate superior skin and enthesitis outcomes; IL-23 inhibitors (guselkumab, risankizumab) offer the highest skin clearance rates; and oral JAK inhibitors (upadacitinib, tofacitinib) provide effective pan-domain coverage — but with additional safety monitoring requirements.

Key messages

Dactylitis + enthesitis + nail disease — the PsA triad
Psoriatic arthritis is clinically distinguished by: dactylitis ("sausage digit" — diffuse inflammatory swelling of an entire finger or toe); enthesitis (tenderness at tendon/ligament insertions — particularly Achilles, plantar fascia, patella tendon); nail involvement (pitting, onycholysis, oil-drop discolouration — present in approximately 80% of PsA patients). These features — absent in rheumatoid arthritis — are the hallmarks that should trigger PsA consideration in any psoriasis patient with joint symptoms.
Affects 20-30% of psoriasis patients — must screen routinely
Approximately 20-30% of psoriasis patients develop PsA. In approximately 60% of cases, skin disease precedes joint disease by an average of 12 years; in 15%, arthritis precedes skin disease; in 15-20% they appear simultaneously. All psoriasis patients should be routinely screened for joint symptoms at every dermatology appointment — the PEST (Psoriasis Epidemiology Screening Tool) questionnaire is validated for this purpose.
Seronegative — RF and anti-CCP negative
PsA is seronegative: rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies are negative in over 95% of PsA patients. Positive RF essentially excludes PsA and supports a diagnosis of RA. PsA can be confused with RA (polyarticular pattern) or ankylosing spondylitis (spinal pattern) — the CASPAR criteria help classification.
IL-17A inhibitors — superior for skin and enthesitis
Anti-IL-17A biologics (secukinumab, ixekizumab) achieve higher skin clearance rates (PASI 90/100) than anti-TNF in psoriasis and are equivalent or superior for joint, nail and enthesitis control. Anti-TNF agents remain widely used first-line biologics with long-term safety data. IL-23 inhibitors (guselkumab, risankizumab) offer the highest skin clearance rates with good joint data.
JAK inhibitors — oral, effective across all PsA domains
Tofacitinib (Xeljanz) and upadacitinib (Rinvoq) are approved oral JAK inhibitors for PsA — effective for joints, skin, enthesitis and dactylitis without the need for injection. Important safety considerations: increased VTE risk (particularly tofacitinib at higher doses); cardiovascular safety concerns in high-risk patients (ORAL Surveillance trial); cancer risk in high-risk populations. JAK inhibitors preferred for patients requiring oral therapy or in whom injection-based biologics have failed.
Axial PsA — a distinct and challenging subtype
Psoriatic spondylitis (axial PsA) — affecting approximately 25-35% of PsA patients — causes inflammatory back pain (morning stiffness, improves with movement) with sacroiliac joint involvement (sacroiliitis on MRI). Clinical differences from ankylosing spondylitis (AS): asymmetric sacroiliitis (AS is typically symmetric); less frequent HLA-B27 positivity (approximately 50% in PsA vs approximately 85-90% in AS); skip lesions; psoriasis and peripheral joint disease co-occurring.

Key statistics

20-30%
of psoriasis patients develop psoriatic arthritis
WHO/EULAR
~80%
of PsA patients have nail involvement (pitting, onycholysis, oil-drop)
EULAR/ACR
~0.1-0.25%
PsA prevalence in general population
WHO/EULAR
CASPAR
Classification Criteria for Psoriatic Arthritis — standard diagnostic tool
Taylor et al. 2006
Seronegative
RF and anti-CCP negative in >95% of PsA (distinguishes from RA)
ACR/EULAR
Upadacitinib
oral JAK inhibitor — effective across all 5 PsA domains (joints, skin, nails, enthesitis, dactylitis)
SELECT-PsA trials

PsA treatment — evidence by domain for key drug classes (EULAR/ACR)

Source: EULAR/ACR 2023. All biologics effective; IL-17A superior for skin/enthesitis; IL-23 highest skin clearance.

Glossary of key terms

CASPAR criteria
Taylor et al. 2006Classification Criteria for Psoriatic Arthritis — validated in 2006. Requires: inflammatory articular disease (joint, spine or enthesis) AND ≥3 points from: current psoriasis (2 points); personal history of psoriasis if no current psoriasis (1 point); family history of psoriasis (1 point); nail dystrophy (pitting, onycholysis — 1 point); negative RF (1 point); current dactylitis (1 point); radiological evidence of juxta-articular new bone formation in hands/feet (1 point). Sensitivity approximately 91.4%, specificity approximately 98.7%.
Dactylitis
EULAR/ClinicalDiffuse inflammatory swelling of an entire digit (finger or toe) — "sausage finger" or "sausage toe." Caused by tenosynovitis (inflammation of the tendons within the digit) plus small joint synovitis. Found in approximately 40-50% of PsA patients; rare in RA. Classified as acute dactylitis (hot, red, tender) or chronic (remains swollen without erythema). Best detected on clinical examination; MRI and US can confirm and quantify. Treatment: responds to anti-TNF, IL-17A inhibitors, JAK inhibitors.
Enthesitis
EULAR/RheumatologyInflammation at the enthesis — the site where tendons, ligaments, fascia or joint capsules insert into bone. A hallmark feature of spondyloarthropathy (PsA, AS, reactive arthritis). Common entheseal sites in PsA: plantar fascia origin (plantar heel pain — "plantar fasciitis" in a young patient may be enthesitis); Achilles tendon insertion; patellar tendon insertion; quadriceps insertion; lateral epicondyle; medial epicondyle. Detected clinically (tenderness on direct pressure at entheseal sites); quantified with the Leeds Enthesitis Index (LEI) or MASES. MRI and US can demonstrate bone marrow oedema and peritendinous inflammation.
Arthritis mutilans
RheumatologyThe most severe and destructive pattern of psoriatic arthritis (approximately 5% of PsA) — characterised by gross osteolysis (bone destruction) of the small joints of hands and feet → telescoping of digits → "opera glass hand" (main en lorgnette). Profoundly disabling; disfiguring; irreversible once established. The x-ray appearance: "pencil-in-cup" deformity (pointed proximal phalangeal end within a cup-shaped excavation of the distal phalanx); "whittled bone" appearance; "bat wing" and "cup and saucer" deformities. Associated with severe systemic disease and often positive HLA-B27.
The ORAL Surveillance trial — JAK inhibitor cardiovascular safety
FDA/NEJM 2022A randomised trial comparing tofacitinib vs TNF inhibitors in RA patients with cardiovascular risk factors. Results: tofacitinib associated with higher rates of: major cardiovascular events (MACE); cancer; VTE vs anti-TNF. Consequences: FDA added black box warning to all JAK inhibitors (tofacitinib, baricitinib, upadacitinib); JAK inhibitors should be used after anti-TNF failure in patients ≥50 years with ≥1 cardiovascular risk factor or other risk factors. This significantly affects JAK inhibitor prescribing in PsA and RA.
Five clinical patterns of PsA
Moll & Wright 1973The original Moll and Wright 1973 classification: (1) Distal interphalangeal (DIP) predominant (~5-10%): DIP joint involvement with nail disease. (2) Asymmetric oligoarthritis (<5 joints, ~35%): asymmetric, large and small joints, often lower limb. (3) Symmetric polyarthritis (~25%): resembles RA clinically; seronegative. (4) Spondyloarthritis (~25%): sacroiliac involvement, inflammatory back pain; asymmetric sacroiliitis. (5) Arthritis mutilans (~5%): most severe; osteolytic destruction. Overlap between patterns is common; patterns may evolve over time. Now partially replaced by domain-based assessment (joints, skin, nails, enthesitis, dactylitis, axial).

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