Abstract
ContextImaging of dactylitis in adult psoriatic arthritis suggests a pathophysiological role for enthesitis. However, histological definition of the dactylitic digit is unavailable.ObjectiveWe evaluated the role of enthesitis in dactylitis associated with psoriatic juvenile idiopathic arthritis (psJIA) in a child who underwent detailed imaging and histologic evaluation.DesignRadiographs, ultrasound and high-resolution magnetic resonance imaging were employed to define the locus of disease in two dactylitic digits from a 14-year-old girl with psJIA. Biopsies were stained with hematoxylin and eosin, CD3, CD20, CD4, CD8 and CD117 and examined via light microscopy.ResultsRadiologic features of dactylitis included enhanced signal at digital entheses without accompanying synovitis or tenosynovitis. Histologically, finger and toe tissue exhibited hypervascular tenosynovium with a fibromyxoid expansion of fibrous tissue. This was accompanied by sparse to moderate perivascular lymphocytic inflammation consisting predominantly of T cells, with occasional admixed B cells and mast cells. Neutrophils and plasma cells were absent. Fibrocartilage exhibited reactive features including increased extracellular myxoid matrix, binucleation, and focal necrosis, without cellular inflammation. Fibrinous synovitis and mild reactive synoviocyte hyperplasia were seen.ConclusionsDactylitis in psJIA bears a radiographic resemblance to the condition in adult psoriatic arthritis. Histologic hallmarks include an expanded mast cell-populated extracellular myxoid matrix, cartilage degeneration, and a T cell-rich perivascular inflammatory infiltrate. These findings help to define enthesitis as a clinicopathologic entity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12969-015-0003-2) contains supplementary material, which is available to authorized users.
Highlights
The classification of juvenile idiopathic arthritis (JIA) is a work in progress [1]
Dactylitis in psoriatic juvenile idiopathic arthritis (psJIA) bears a radiographic resemblance to the condition in adult psoriatic arthritis
These findings have implications for the classification of childhood arthritides. They suggest a pathogenic continuity of psJIA with adult (Adult) psoriatic arthritis (PsA), where enthesitis is recognized as a canonical clinical feature, and dactylitis is a highly specific physical finding [20]
Summary
The classification of juvenile idiopathic arthritis (JIA) is a work in progress [1]. Among the categories of JIA recognized by the International League of Associations for Rheumatology (ILAR), psoriatic JIA (psJIA) presents a particular diagnostic challenge [2,3]. A key clinical feature recognized to favor the diagnosis of psJIA is dactylitis, defined as sausage-like or fusiform swelling of a finger or toe that extends beyond the joint margins to encompass the entire digit [6]. In pediatric rheumatology, arthritis with enthesitis in the absence of frank psoriasis is usually grouped under the term enthesitis-related arthritis (ERA) [1]. This distinction implies that enthesitis is not a core feature of psoriatic arthritis in children. If dactylitis in children were shown to reflect enthesitis in a radiographic or histological manner, this would highlight the challenge of drawing a clear demarcation between psJIA and ERA
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
