Multiple endocrine neoplasia (MEN) - An overview and case report - Patientwith sporadic bilateral pheochromocytoma, hyperparathyroidism and marfanoid habitus

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 int o MEN IIa and MEN IIb. The syndromes are characterized by benign and malign ant changes in two or more endocrine organs, as wed as incidental changes i n nervous, muscular and connective tissue. Two main forms can be distinguis hed: the MEN-I syndrome with hyperplasia of the parathyroid gland, accompan ied by islet cell tumor and pituitary adenoma; the MEN-II syndrome with med ullary thyroid carcinoma in combination with bilateral pheochromocytoma and hyperplasia of the parathyroid gland (MEN IIa), while type IIb is characte rized by the additional appearance of neurocutaneous manifestations without primary hyperparathyroidism. Characteristics shared by these syndromes inc lude the involved cell type, most of the tumors are composed of one or more specific polypeptide- and biogenic amine-producing cell types (APUD - amin e precursor uptake and decarboxylation). The second characteristic is the i ncreased incidence in certain families. The hereditary component is autosom al dominant with variable expression but high penetrance. Mechanisms of tum origenesis 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 chr omosome ii, MEN II is caused by activation of the RET proto-oncogene. We ha ve reported the case of a young man exhibiting bilateral pheochromocytoma. In addition, the patient showed mild primary hyperparathyroidism and marfan oid 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 descr ibed here are not related to multiple endocrine neoplasia syndromes.