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

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. 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. 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. 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.