Clinical insights into heterogeneity of rheumatoid factor negative polyarticular juvenile idiopathic arthritis across the world. - Naddei, Roberta; Burrone, Marco; Ridella, Francesca; Uziel, Yosef; Trachana, Maria; Dolezalova, Pavla; Rumba-Rozenfelde, Ingrida; Ruperto, Nicolino; Ravelli, Angelo; Consolaro, Alessandro (Pediatric Rheumatology, 2025)