Multiple endocrine neoplasia (MEN)--an overview and case report--patient with sporadic bilateral pheochromocytoma, hyperparathyroidism and marfanoid habitus.Anticancer Res. 2000 Nov-Dec; 20(6C):4877-87.AR
The multiple endocrine neoplasia syndromes are divided into two categories: MEN type I and MEN type II. The MEN type II syndrome is further divided into MEN IIa and MEN IIb. The syndromes are characterized by benign and malignant changes in two or more endocrine organs, as well as incidental changes in nervous, muscular and connective tissue. Two main forms can be distinguished: the MEN-I syndrome with hyperplasia of the parathyroid gland, accompanied by islet cell tumor and pituitary adenoma; the MEN-II syndrome with medullary thyroid carcinoma in combination with bilateral pheochromocytoma and hyperplasia of the parathyroid gland (MEN IIa), while type IIb is characterized by the additional appearance of neurocutaneous manifestations without primary hyperparathyroidism. Characteristics shared by these syndromes include the involved cell type, most of the tumors are composed of one or more specific polypeptide- and biogenic amine-producing cell types (APUD--amine precursor uptake and decarboxylation). The second characteristic is the increased incidence in certain families. The hereditary component is autosomal dominant with variable expression but high penetrance. Mechanisms of tumorigenesis differ in these syndromes. While MEN I is caused by an inherited mutation of a tumor suppressor gene, menin, located on the long arm of chromosome 11, MEN II is caused by activation of the RET proto-oncogene. We have reported the case of a young man exhibiting bilateral pheochromocytoma. In addition, the patient showed mild primary hyperparathyroidism and marfanoid habitus, all these stigmata usually being part of the MEN-II syndrome. Although this described patient showed a phenotypic mixture of the MEN-IIa and MEN-IIb syndrome, the genetic analysis for MEN II and von-Hippel-Lindau gene did not reveal any pathologic mutations, the endocrine disorders described here are not related to multiple endocrine neoplasia syndromes.