The multiple endocrine neoplasia (MEN) syndromes comprise 4 genetically distinct familial diseases involving adenomatous hyperplasia and malignant tumors in several endocrine glands.
MEN 1 involves primarily hyperplasia or sometimes adenomas of the parathyroid glands (with resultant hyperparathyroidism) and tumors of the pancreatic islet cells and/or pituitary gland.
MEN 2A involves primarily medullary thyroid carcinoma, pheochromocytoma, hyperplasia or sometimes adenomas of the parathyroid glands (with resultant hyperparathyroidism), and occasionally cutaneous lichen amyloidosis.
MEN 2B involves primarily medullary thyroid carcinoma, pheochromocytoma, multiple mucosal and intestinal neuromas, and marfanoid habitus.
MEN 4 involves primarily adenomas and sometimes hyperplasia of the parathyroid glands (with resultant hyperparathyroidism) and tumors of the pancreatic islet cells and/or pituitary gland.
Clinical features depend on the glandular elements involved. The phenotype of MEN 4 is similar to that of MEN 1 but lacks the cutaneous abnormalities seen in the latter disorder.
Each syndrome is inherited as an autosomal dominant trait with a high degree of penetrance, variable expressivity, and production of seemingly unrelated effects by a single mutant gene. The specific mutation is not always known.
Symptoms and signs develop at any age. Proper management includes early identification of affected individuals within a kindred and surgical removal of the tumors when possible. Although these syndromes are genetically and clinically distinct, significant overlap exists (see table Conditions Associated With MEN Syndromes).
