Abstract
Background: Despite being considered as a distinct diagnostic category in the current ILAR classification criteria, Juvenile Psoriasic Arthritis (JPsA) is known to be a heterogeneous clinical entity, with growing evidence suggesting at least two age-based distinct subgroups(1) Objectives: To identify and characterize subgroups of patients classified as JPsA according to the ILAR criteria and their possible differences in outcomes. Methods: Cross-sectional data from patients enrolled in The EPidemiology, treatment and Outcome of Childhood Arthritis (EPOCA) study and classified as JPsA according to ILAR criteria (n=308) were analyzed. Latent class analysis (LCA) was used to identify subgroups of subjects with similar profiles ILAR criteria for JPsA (presence at onset of psoriasis, dactylitis, nail changes, first-degree relative with psoriasis) and age of arthritis onset. Multinomial logistic regression (three-step method) was performed to explore differences across the obtained classes in clinical-laboratoristic features at onset and outcomes measures collected at visit, namely JADAS scores, VAS-measured Pain, Overall Well-Being (PGA) Pediatric Rheumatology Quality of Life Scale (PRQL). In patients with disease duration more than 2 years (n=233), the relation with Articular and Extraarticular Juvenile Arthritis Damage Index (JADI) was also assessed. Results: LCA revealed 5 classes: 1) late-onset patients with psoriasis, characterized by higher frequency of axial involvement at visit (n = 121); 2) early-onset patients with psoriasis, more likely to be ANA-positive (n = 66); 3) young females with dactylitis at onset and family history of psoriasis, more likely to present with symmetric joint involvement (n = 62); 4) subjects with nail changes and family history of psoriasis(n=34); 5) patients exhibiting dactylitis and nail changes at onset, mostly males, with higher rates of HLA-B27 positivity, small joint involvement and enthesitis at visit (n = 25). Class 1 is associated with higher scores of JADAS10, pain, PGA and JQ; these group also shows higher JADI-A than Class 3. Extraarticular damage is worst for Class 2 subjects. Conclusion: The data driven clustering approach revealed several subgroups, confirming the heterogeneity of JPSA in a multinational cohort. Later-onset subjects with psoriasis have more aggressive disease, being clearly distinct from early-onset ANA-positive patients with psoriasis. The results suggest the need to revise the current classification in order to identify groups that may benefit from different therapeutic choices.