Multiple Endocrine Neoplasia Type 1 (MEN1)

Abstract

Multiple endocrine neoplasia (1–3) is characterized by the occurrence of tumors involving two or more endocrine glands within a single patient. The disorder has previously been referred to as multiple endocrine adenopathy (MEA) or the pluriglandular syndrome. However, glandular hyperplasia and malignancy may also occur in some patients and the term multiple endocrine neoplasia (MEN) is now preferred. There are two major forms of multiple endocrine neoplasia referred to as type 1 and type 2 and each form is characterized by the development of tumors within specific endocrine glands (see Table 1). Thus, the combined occurrence of tumors of the parathyroid glands, the pancreatic islet cells, and the anterior pituitary is characteristic of multiple endocrine neoplasia type 1(MEN1), which is also referred to as Wermer’s syndrome. In addition to these tumors, adrenal cortical, carcinoid, facial angiofibromas, collagenomas, and lipomatous tumors have also been described in patients with MENI (3, 4). However, in multiple endocrine neoplasia type 2 (MEN2), which is also called Sipple’s syndrome, medullary thyroid carcinoma (MTC) occurs in association with phaeochromocytoma, and three clinical variants referred to as MEN2a, MEN2b and MTC-only are recognized (1, 5). In MEN2a, which is the most common variant, the development of MTC is associated with phaeochromocytoma and parathyroid tumors. However, in MEN2b parathyroid involvement is absent and the occurrence of MTC and phaeochromocytoma is found in association with a marfanoid habitus mucosal neuromas, medullated corneal fibers and intestinal autonomic ganglion dysfunction leading to a megacolon.