Patients with the multiple endocrine neoplasia type 1 (MEN1) syndrome (OMIM ID: 131100) carry germline heterozygous loss-of-function mutations in the MEN1 gene which predisposes them to the development of various endocrine and non-endocrine tumors (Chandrasekharappa et al. 1997, Lemmens et al. 1997). Here, MEN1 is linked to multiple endocrine neoplasia type 1.