AbstractBehçet’s syndrome (BS) represents an understudied topic in pediatrics: the main aims of our study were to characterize demographic and clinical features of a cohort of BS patients with juvenile-onset managed in three tertiary referral centers in Italy, evaluate their evolution in the long-term, and detect any potential differences with BS patients having an adult-onset. Medical records of 64 juvenile-onset and 332 adult-onset BS followed-up over a 2-year period were retrospectively analyzed and compared. Mean age ± SD of first symptom-appearance was 10.92 ± 4.34 years with a female-to-male ratio of 1.06:1. Mucocutaneous signs were the most frequent initial manifestations, followed by uveitis. Throughout the disease course, genital aphthae (76.56%) and pseudofolliculitis (40.63%) prevailed among the mucocutaneous signs, while major organ involvement was represented by gastrointestinal and ocular involvement (43.75 and 34.38%, respectively). No significant differences emerged for both mucocutaneous signs and specific major organ involvement between juvenile-onset and adult BS patients. After excluding nonspecific abdominal pain, juvenile-onset BS patients were less frequently characterized by the development of major organ involvement (p = 0.027). Logistic regression detected the juvenile-onset as a variable associated with reduced risk of long-term major organ involvement (OR 0.495 [0.263–0.932],p = 0.029). In our cohort, juvenile-onset BS resembled the clinical spectrum of adult-onset patients. Pediatric patients with a full-blown disease at onset showed a more frequent mucocutaneous involvement. In addition, patients with juvenile-onset seemed to develop less frequently major organ involvement and had an overall less severe disease course.