Enthesitis in Spondyloarthritis. From pathogenesis to clinical presentation and imaging: Similarities and differences between PsA and axSpA

Radiographic axial spondyloarthritis (r-axSpA), non-radiographic axial spondyloarthritis (nr-axSpA), and psoriatic arthritis (PsA) represent distinct yet overlapping entities within the spondyloarthritis (SpA) spectrum. Enthesitis has emerged as a unifying hallmark of these diseases, linking mechanical stress, immune dysregulation, and structural remodeling. Understanding similarities and differences in entheseal pathology among these entities may elucidate shared and divergent mechanisms driving disease pathogenesis and progression. Mechanical stress at entheses activates mechanosensitive pathways leading to inflammatory changes and eventually new bone formation. In both research and clinical practice, enthesitis is assessed though the use of clinical indices and imaging modalities, particularly ultrasound and Magnetic Resonance Imaging (MRI), while modern modalities emerge on. Despite shared inflammatory mechanisms, variations in cytokine profiles, soft tissue and underlying bone involvement drive disease-specific patterns of damage and repair in axial and peripheral sites. Combining standardized multimodal imaging with molecular biomarkers holds promise for refining classification, improving early diagnosis, and guiding targeted therapeutic strategies across the SpA spectrum. In this review we explore enthesitis from various standpoints, including pathophysiology, clinical and imaging approaches under the prism of the similarities and differences between PsA and AxSpA. • Enthesitis is the primary pathological lesion in the SpA spectrum. • Enthesitis links mechanical stress to immune dysregulation in SpA. • PsA targets the SEC, while axSpA is driven by bone marrow inflammation. • Enthesitis correlates with higher disease burden and fatigue. • Biomarkers combined with imaging may guide precision medicine.