Epidemiology

MEN syndromes are relatively rare.

MEN1

  • Estimated prevalence is between 1 to 3 in 100,000.[8]

  • Around 90% of patients develop primary hyperparathyroidism (PHPT) and this is often diagnosed at a younger age (20 to 25 years) compared to sporadic forms of PHPT.[3]

  • Approximately 40% to 70% of patients with MEN1 have pancreatic neuroendocrine tumors (NETs), which may be functioning (e.g., gastrinomas, insulinomas, glucagonomas, vasoactive intestinal polypeptidomas [VIPomas]), or nonfunctioning.[3] Due to routine screening in MEN1 families, nonfunctioning pancreatic NETs are now the most common type of pancreatic NET in the setting of MEN1.[3][8] Gastrinomas are the most common functioning duodenopancreatic NETs in MEN1, affecting 21% to 70% of patients.[8]

  • Around 30% to 40% of patients with MEN1 have pituitary adenomas.[3]

  • Prolactinomas are the most common and occur in 65% of patients with MEN1-related pituitary adenomas.[8] Growth hormone-secreting (somatotroph) pituitary adenomas and nonfunctioning adenomas are the next most common MEN1-related pituitary adenomas.[8] Adrenocorticotrophic hormone-secreting tumors are less common, occurring in <5% of patients with MEN1-related pituitary adenomas.[8] Thyroid-stimulating hormone-secreting tumors and gonadotroph secreting tumors are rare (<1%) MEN1-related pituitary adenomas.[8]

  • Thymic and bronchial neuroendocrine tumors (NETs) each occur in 2% of patients with MEN1.[3] Thymic NETs show a marked male predominance in European patients with MEN1 and are associated with a high mortality.[8] Bronchial NETs have a more indolent course.[3][9][10]

MEN2A and MEN2B

  • Reported in approximately 1000 families worldwide in 2001.[5]

  • Most cases are MEN2A.

  • Medullary thyroid cancer presents in nearly all genetic carriers of MEN2 by adulthood if not treated with prophylactic thyroidectomy, and is the commonest presenting feature of MEN2.[5]

  • Pheochromocytoma occurs in about 50% of MEN2A patients. Pheochromocytoma is the first manifestation of MEN2 in 25% of patients.[5][11]

  • Multigland parathyroid adenomas develop in up to 30% of MEN2A patients.[5][12][13][14]

  • PHPT is found in smaller subsets of MEN2A patients.[15]

  • Rare variants of MEN2A include Hirschsprung disease and cutaneous lichen amyloidosis.[16][17]

  • MEN2B is quite rare (prevalence: 0.9 to 1.6 per million individuals) and, compared with MEN2A, is notable for more aggressive pheochromocytoma and medullary thyroid cancer presenting at earlier ages.[6][18]

MEN4

  • MEN4 is rare, with only a small number of cases published worldwide since it was first described. The main features are parathyroid adenomas and pituitary adenomas.[19]

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