Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia is a genetic endocrine tumor syndrome characterized by the presence of medullary thyroid carcinoma (MTC), pheochromocytoma, and hyperparathyroidism. There are two major variants. Multiple endocrine neoplasia (MEN) type 2A or Sipple syndrome has three clinical features: MTC, pheochromocytoma, and hyperparathyroidism; MEN2B has a different phenotype: MTC, pheochromocytoma, mucosal neuromas distributed throughout the mouth and gastrointestinal tract, and Marfanoid features including long thin arms and legs, an altered upper/lower body ratio, and pectus abnormalities. These clinical syndromes are caused by specific activating mutations of the RET tyrosine kinase receptor, important in neurological development of the gastrointestinal tract. MEN2 is one of a handful of genetic syndromes where the identification of a mutation leads to a specific action. Children with germline activating mutations of RET are treated in early childhood with a total thyroidectomy to prevent the development of metastatic MTC.