Pathogenesis and Diagnosis of Psoriatic Arthritis

Abstract

Introduction: Psoriatic arthritis (PsA) is a chronic, heterogeneous inflammatory disease closely associated with psoriasis of the skin and nails. Its clinical manifestations are diverse, involving peripheral joints, the axial skeleton, entheses (sites where tendons or ligaments attach to bone), and various extra-articular sites, making its diagnosis a significant clinical challenge.

Methods: This is a narrative review of recent literature focusing on the complex pathogenesis and evolving diagnostic strategies for PsA. The review synthesizes information on genetic, immunological, and environmental factors, as well as the role of modern imaging and laboratory findings in accurate diagnosis.

Results: The pathogenesis of PsA arises from a complex interplay of genetic predisposition (such as HLA-B27), immunological pathways, and environmental triggers like mechanical stress and infections. The activation of both the innate and adaptive immune systems, particularly the IL-23/IL-17 axis, is central to driving the chronic inflammation and joint damage characteristic of the disease. Diagnosing PsA is often difficult due to its overlapping features with other inflammatory arthritides. The Classification Criteria for Psoriatic Arthritis (CASPAR) are widely used and incorporate evidence of psoriasis, specific patterns of joint involvement, dactylitis, and characteristic radiological changes. Imaging modalities are crucial for an early and accurate diagnosis: conventional radiography detects classic erosions and new bone formation, ultrasonography is sensitive for evaluating synovitis and enthesitis, and MRI is excellent for identifying early inflammatory changes in both axial and peripheral joints. Laboratory tests, such as a negative rheumatoid factor and anti-CCP, are key to differentiating PsA from rheumatoid arthritis.

Conclusions: A comprehensive understanding of the pathogenesis and diagnostic strategies for PsA is essential for early recognition, which is critical for preventing disease progression and selecting the most appropriate therapy. This review highlights current insights that can serve as a foundation for improved clinical practice in managing this complex disease.