An Unusual Kindred of the Multiple Endocrine Neoplasia Type 1 (<i>MEN1</i>) in Japanese¹

Abstract

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant predisposition to hyperplasia/tumor of the parathyroid glands, endocrine pancreas, and anterior pituitary (1). Recently, the MEN1 gene, which had been mapped to chromosomal region 11q13 (2), was identified by positional cloning (3). The MEN1 gene, which is composed of 10 exons, encodes a 610-amino acid protein (menin) (3). Germ line mutations of the MEN1 gene were detected at high frequency in both familial and sporadic cases of MEN 1 in Caucasians (3–8) and in other ethnic groups, including Japanese (9–12). The prevalence of pituitary adenomas in patients with MEN 1 is very variable, ranging from 15–60% (13–15). This wide range of values presumably depends on different methodological approaches. Of the various subtypes of pituitary adenomas, prolactinomas are most commonly seen in association with the MEN 1, followed by GH-secreting adenomas, ACTH-secreting adenomas, and nonfunctioning adenomas (14–16). In several pedigrees, many affected members with pituitary adenomas were found to have only prolactinomas (17–19). There is a distinct phenotype of MEN 1 in which a prolactinoma and hyperparathyroidism are dominant manifestations and a pancreatic endocrine tumor is rare. The phenotype is termed “the prolactinoma variant of MEN 1” (19–21). The prolactinoma variant of MEN 1, referred to as MEN 1Burin, was described in one Newfoundland family (19, 20), one family from Pacific Northwest (18), and one other family (21). Of 83 affected family members of MEN 1Burin, 93% had parathyroid tumors, 37% had prolactinoma, and 2.5% had gastrinoma (21). One of the eight affected individuals in the Pacific Northwest family, 100% had parathyroid tumors, 75% had prolactinoma, and 12% had gastrinoma (21). Genetic analysis of families from MEN 1Burin and Pacific Northwest disclosed that the patients have the germ line mutation of MEN1 gene (4, 20). We describe in this study one Japanese unusual MEN 1 kindred in which the four of five mutation carriers were affected and have developed prolactinoma.