Juvenile psoriatic arthritis (JPsA) accounts for 1–7% of all cases of juvenile idiopathic arthritis (JIA) and its definition has been a matter of controversy among pediatric rheumatologists for many years. The traditional attribution of JPsA to the spondyloarthropathy group was challenged in the early 1990s, whereas the recent demonstrations of its heterogenous nature have led to questions about its identification as a distinct category in JIA classification. It has been shown that children with the phenotype of JPsA can be divided in two subgroups, one presenting with the features of early-onset ANA-positive JIA, and another that belongs to the spectrum of spondyloarthropathies. The few studies that have compared the clinical characteristics and genetic determinants of JPsA with those of the other JIA categories have obtained contrasting findings. The debate on the categorization of JPsA as a distinct entity within JIA classification is still ongoing and has prompted the revision of its current classification.

Enthesitis-related arthritis (ERA) represents 5–30% of all cases of juvenile idiopathic arthritis (JIA) and belongs to the spectrum of the disorders included in the group of juvenile spondyloarthritis. In the last decade, there have been considerable advances in the classification, diagnosis, monitoring, and treatment of ERA. New provisional criteria for ERA have been recently proposed by the Paediatric Rheumatology INternational Trials Organisation, as part of a wider revision of the International League of Associations for Rheumatology criteria for JIA. The increased use of magnetic resonance imaging has shown that a high proportion of patients with ERA present a subclinical axial disease. Diverse instruments can be used to assess the disease activity of ERA. The therapeutic recommendations for ERA are comparable to those applied to other non-systemic JIA categories, unless axial disease and/or enthesitis are present. In such cases, the early use of a TNF-alpha inhibitor is recommended. Novel treatment agents are promising, including IL-17/IL-23 or JAK/STAT pathways blockers.

To our knowledge, limited information is available about the differences in the characteristics of rheumatoid factor (RF)-negative polyarticular juvenile idiopathic arthritis (JIA) throughout the world. This study was aimed to compare the demographic and clinical features of patients with RF-negative polyarthritis across the world. Patients were part of a multinational sample included in a study aimed to investigate the prevalence of disease categories, treatment regimens, and disease status in patients from different geographical areas (EPOCA Study). All patients underwent a retrospective assessment, based on the review of clinical chart, and a cross-sectional evaluation, which included assessment of physician- and parent-reported outcomes and collection of ongoing medications. Among the 9081 patients enrolled in the EPOCA study, 2141 patients (23.6%) with RF-negative polyarthritis were included in the present analysis. The prevalence of RF-negative polyarthritis was highest in North America and lowest in Southeast Asia (12.7%). The age at disease onset was lower in Northern and Southern Europe, where the highest prevalence of uveitis was found. Uveitis was rare in Southeast Asia, Africa & Middle East and Latin America. Patients from Eastern Europe, Latin America and Africa and Middle East presented with the highest prevalence of active joints at the visit. The combination of early onset, ANA positivity, and uveitis was observed mainly in Southern Europe (39%). Our results confirm the wide heterogeneity of the clinical presentation and outcome of children with RF-negative polyarticular JIA throughout the world. In particular, relevant differences in the onset age were observed across geographic areas. The group of children with early onset polyarthritis, ANA positivity, and risk of uveitis is remarkably frequent in Southern Europe.

Objectives: The objective of this study was to develop and test a composite DAS for JDM solely based on parent-reported outcomes (PROs). Methods: The parent JDM Activity Index (ParJDMAI) includes the following four PROs: (1) global assessment of disease activity; (2) assessment of fatigue; (3) assessment of muscle disease activity; (4) assessment of skin disease activity. Each item is weighted on a 0–10 scale, which yields a total score ranging from 0 to 40. Validation procedures were conducted on a multicentre sample of 254 patients with JDM according to the OMERACT filter for outcome measures in rheumatology. Results: The ParJDMAI is short and simple, and is quick, taking <10 minutes to complete and score, which makes it practical for use in standard clinical care. In validation analyses, the tool demonstrated good construct validity, satisfactory internal consistency (Cronbach’s alpha 0.86) and structure (with unambiguous identification of one factor with eigenvalue 2.9 on exploratory factor analysis), strong ability to discriminate between physician-estimated disease activity states (P < 0.001), and fair responsiveness to clinically important change over time (standardized response mean 0.8 among patients judged as improved by the parents). The ParJDMAI correlated strongly with physician-centred measures of disease activity. Conclusion: The ParJDMAI was found to be feasible and to possess good measurement properties. It also proved to potentially serve as a surrogate for physicians’ evaluations. Completion of the ParJDMAI through digital technologies may provide a reliable and pragmatic approach for building a remote patient-monitoring program.