Psoriatic spectrum arthritis in children: a multicentre observational study for a new definition of Juvenile Psoriatic Arthritis

Abstract

Abstract Background:The definition of psoriatic arthritis in pediatrics (JPsA) is controversial. The study purpose to describe clinical and laboratory characteristics and responses to therapies in children with psoriatic arthropathies. Methods: A retrospective multicentre observational study enrolling subjects meeting the ILAR criteria for juvenile psoriatic arthritis. We also included subjects meeting the enthesitis-related arthritis criteria, except for the presence of psoriasis and/or family history of psoriasis or psoriatic arthritis in a first-degree relative. Disease remission was defined according to the Wallace criteria. Results: 71 patients (44 females, 27 males). Disease onset was before 10 years in 32 patients (median 5.5 years) and after 10 years (median 13 years) in 39. Inflammation indexes and antinuclear antibodies were raised, respectively, in 61% and 47% of the tested patients. Twenty patients (28.2%) got clinical remission with intra-articular glucocorticoids. Eighteen patients (25.3%) with synthetic disease-modifying anti-rheumatic drugs got better, and 33 patients (46.5%) with biological DMARDs. Two patients presented with intractable uveitis. Fifty-five patients (77.5%) met the ILAR criteria for JPsA; eight were HLA B27+ males with disease onset over 6 years of age, and eight had arthritis and enthesitis. Four clinical patterns were found using unsupervised principal component analysis. One of them was mostly made up of early-onset oligoarticular arthiritis, dactylitis, tenosynovitis, and uveitis. The two groups occurring after 10 years of age were more similar to adult-onset psoriatic arthritis or undifferentiated spondyloarthropaties. Conclusions: Post-pubertal clusters of JPsA are similar to typical adult PsA, while peculiar clusters are identified in younger children.