Type I interferon signature as a possible new marker for stratification of patients with juvenile idiopathic arthritis

Objectives: The interferon score (IS) quantifies the expression of interferon-stimulated genes in peripheral blood, providing an indirect estimate of interferon-mediated inflammation in rheumatological disorders. This study explores the clinical significance of IS among a cohort of patients affected by juvenile idiopathic arthritis (JIA) and its relevance to disease stratification and prognosis. Methods: All patients referred to the Rheumatology Service of the Institute for Maternal and Child Health IRCCS Burlo Garofolo, Trieste, Italy, with a diagnosis of JIA (2001 ILAR criteria) were consecutively recruited. Systemic JIA was excluded. Demographic, clinical and laboratory data were collected for each patient in a structured database. Categorical variables were expressed as numbers (%) and compared by the χ2 test or Fisher's exact test. Principal Component Analysis (PCA) was performed with clinical and laboratory data. Results: Forty-four patients were recruited (35 F, 9 M): 19 polyarticular, 13 oligoarticular, 6 oligoarticular-extended, 5 psoriatic and 1 enthesitis-related arthritis. Sixteen had a positive IS (≥3). Increased IS correlated with a higher number of involved joints ≥5 (p=0.013), increased erythrocyte sedimentation rate (ESR) (p=0.026) and hypergammaglobulinaemia (p=0.003). PCA highlighted a subgroup of patients who shared high levels of IS, ESR, C-reactive protein, hypergammaglobulinaemia, JADAS-27, polyarticular involvement and family history of autoimmunity. Conclusions: Although based on a small case series, our results may support the role of IS in better defining a subgroup of JIA subjects with stronger autoimmune features. The possible relevance of these results for therapeutic stratification remains to be explored.