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.