Multiple endocrine neoplasia type 1

Abstract Multiple endocrine neoplasia (1, 2) is characterized by the occurrence of tumours 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 tumours within specific endocrine glands (Table 6.11.1). Thus, the combined occurrence of tumours of the parathyroid glands, the pancreatic islet cells, and the anterior pituitary is characteristic of multiple endocrine neoplasia type 1 (MEN 1), which is also referred to as Wermer’s syndrome. However, in multiple endocrine neoplasia type 2 (MEN 2), which is also called Sipple’s syndrome, medullary thyroid carcinoma (MTC) occurs in association with phaeochromocytoma, and three clinical variants, referred to as MEN 2a, MEN 2b and MTC-only, are recognized (Table 6.11.1). Although MEN 1 and MEN 2 usually occur as distinct and separate syndromes as outlined above, some patients occasionally may develop tumours that are associated with both MEN 1 and MEN 2. For example, patients suffering from islet cell tumours of the pancreas and phaeochromocytomas or from acromegaly and phaeochromocytoma have been described, and these patients may represent ‘overlap’ syndromes. All these forms of MEN may either be inherited as autosomal dominant syndromes or they may occur sporadically, i.e. without a family history. However, this distinction between sporadic and familial cases may sometimes be difficult as in some sporadic cases the family history may be absent because the parent with the disease may have died before developing symptoms. In this chapter, the main clinical features and molecular genetics of the MEN 1 syndrome will be discussed.