MEN1 Disease Occurring Before 21 Years Old: A 160-Patient Cohort Study From the Groupe d'étude des Tumeurs Endocrines

Various MEN1 lesions occurred frequently before 21 years old, but mainly after 10 years of age. Rare, aggressive tumors may develop at any age. Hyperparathyroidism was the most frequently encountered lesion but was not always the first biological or clinical abnormality to appear during the course of MEN1.