Nature Reviews Rheumatology | 2019
Pathophysiology, assessment and treatment of psoriatic dactylitis
Abstract
Dactylitis is diffuse swelling of the digits that is usually related to an underlying inflammatory or infiltrative disorder. Psoriatic arthritis (PsA) is the most common severe disease thought to cause dactylitis. Our understanding of the pathogenesis of PsA-related dactylitis comes from experimental animal models of PsA-like disease, as well as advances in imaging and other clinical studies. Clinical trials in PsA have increasingly included dactylitis as an important secondary outcome measure. These studies indicate that cytokines drive multi-locus microanatomical pan-digital pathology. Given the importance of pro-inflammatory cytokines, the pathogenesis of dactylitis is best understood as an initial aberrant innate immune response to biomechanical stress or injury, with subsequent adaptive immune mechanisms amplifying the dactylitis inflammatory response. Regarding the treatment of dactylitis, no studies have been conducted using dactylitis as the primary outcome measure, and the current knowledge comes from analysis of dactylitis as a secondary outcome measure.Dactylitis is diffuse inflammation of the digits and is so closely associated with psoriatic arthritis that it can be used as an outcome measure of it. In this Opinion article, the authors describe how imaging modalities and scoring systems combined with data from animal models can be used to understand the underlying anatomy and immunopathogenesis of dactylitis.