Clinical features of MEN1 in children, adolescents, and young adults: a single-center study.

Background: Multiple endocrine neoplasia type 1 (MEN1) can present during childhood and adolescence, yet data on the full endocrine and non-endocrine phenotype in young patients remain limited. Methods: We conducted a retrospective single-center study of genetically confirmed MEN1 patients diagnosed at ≤21 years and followed between 2001 and 2024. Clinical features, surveillance findings, treatments, and outcomes were extracted from medical records. Results: The cohort included 21 patients (52% males), with a median age at genetic diagnosis of 15 years and a median follow-up of 9 years. At first evaluation, 33% were asymptomatic Conclusions: In MEN1 patients diagnosed at ≤21 years, early disease expression is common and clinically meaningful. PHPT represents the earliest and most prevalent manifestation and is frequently associated with renal and skeletal morbidity despite sometimes mild biochemical abnormalities. GEP-NETs and pituitary adenomas are also prevalent by late adolescence/young adulthood and are often indolent, suggesting structured, age-adapted multidisciplinary surveillance and early cascade genetic testing in at-risk families.