Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant hereditary disease due to a mutation in the MEN1 tumor suppressor gene. The risk of the disease in first-degree relatives of MEN1 mutation carriers is 50%. MEN1 gene mutations are not identified in 10-30% of familiar MEN1 patients and in 60-80% of sporadic MEN1 cases, which can be explained by mutations in the noncoding regions of the MEN1 gene, large gene deletions or mutations in other yet unknown genes. Molecular genetic testing can exclude the diagnosis of MEN1 in patients who do not harbor the MEN1 mutation, thus revealing a MEN1 phenocopy. This obviates the need for annual screening for the early detection of other remaining components of the disease and its risk in progeny.