MEN type 2

• MEN 2:

  • Autosomal dominant
  • Mutation of the RET proto-oncogene
  • Primary hyperparathyroidism
  • Medullary thyroid cancer
  • Phaeochromocytoma
• • MEN 2A: normal appearance, primary hyperparathyroidism is common.
  • MEN 2B: marfanoid habitus, primary hyperparathyroidism is rare.
• In MEN 2 phaeochromocytomas are bilateral in around 60% of cases as opposed to 10% of sporadic cases. They are rarely malignant and tend to occur in the second to third decades of life.
• Medullary thyroid cancer occurs in almost all patients with MEN 2. The disease is characteristically bilateral and multifocal in MEN 2, as opposed to unilateral disease seen in sporadic cases.

  Due to high penetrance, prophylactic surgery is indicated in all patients with MEN 2.
• MEN 2A is defined by the identification of the RET oncogene mutation or the presence of two or more of the characteristic tumour types. Genetic testing is always indicated in index cases.
• Those who present with MTC should be screened for phaeochromocytomas with plasma fractionated metanephrines and hyperparathyroidism with serum calcium.
• Prophylactic thyroidectomy is indicated in patients with confirmed MEN 2.
• Phaeochromocytomas must be managed surgically with either unilateral or bilateral adrenalectomy.

  Those receiving a bilateral adrenalectomy require glucocorticoid and mineralocorticoid replacement to manage the resulting adrenal insufficiency.