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multiple-endocrine-neoplasia-type-2

Multiple Endocrine Neoplasia Type 2

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What is multiple endocrine neoplasia type 2?

Multiple endocrine neoplasia type 2 (MEN2) is a hereditary condition associated with three primary types of tumors: medullary thyroid cancer, parathyroid tumors, and pheochromocytoma. MEN2 is classified into three subtypes based on clinical features.

(a) MEN2A, which affects 60% to 90% of MEN2 families

(i) Medullary thyroid cancer: 98-100% with MEN2A are affected

(ii) Pheochromocytoma (a typically benign (noncancerous) tumor of the adrenal glands):     50% with MEN2A affected

(iii) Parathyroid adenoma (benign tumor) or hyperplasia (increased size) of the parathyroid gland: 5-10% with MEN2A affected

(b) MEN2B, which affects 5% of MEN2 families  

(i) Medullary thyroid cancer: 98-100% with MEN2B affected

(ii) Pheochromocytoma: 50% with MEN2B affected

(iii) Mucosal neuroma (benign tumor of nerve tissue on the tongue and lips): 95-98%      affected

(iv) Digestive problems: 75-90% affected

(v) Muscle, joint, and spinal problems: 95% affected

(vi) Typical facial features, including swollen lips and thick eyelids: 75-90% affected

 (c) Familial medullary thyroid cancer (FMTC), which affects 5% to 35% of MEN2 families

 (i) Medullary thyroid carcinoma only

Sources:  Gagel RF, Marx SJ. “Multiple endocrine neoplasia.” Williams Textbook of Endocrinology, Chapter 40, 11th ed., Philadelphia, 2008, and Eng C, Clayton D, et al. “The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis.” JAMA 276(19):1575-9, 11/1996.

What causes MEN2?

MEN2 is a genetic condition. This means that the cancer risk and other features of MEN2 can be passed from generation to generation in a family. The gene associated with MEN2 is called RET. A mutation (alteration) in the RET gene gives a person an increased risk of developing medullary thyroid cancer and other tumors associated with MEN2.

How is MEN2 inherited? 

Normally, every cell has two copies of each gene: one inherited from the mother and one inherited from the father. MEN2 follows an autosomal dominant inheritance pattern, in which a mutation (a change in the DNA sequence that alters the protein sequence) happens in only one copy of the gene. This means that a parent with a gene mutation may pass along a copy of their normal gene or a copy of the gene with the mutation. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation. A brother, sister, or parent of a person who has a mutation also has a 50% chance of having the same mutation. If a child inherits the mutated RET gene from an affected parent, there is almost a 100% chance of developing medullary thyroid cancer and less probabilities of developing other symptoms of this syndrome during his or her lifetime.

How common is MEN2?

It is estimated that about one in 30,000 people has MEN2. Most people with MEN2B do not have any family history of the condition. They have a de novo (new) mutation in the RET gene. Fewer than 5% of people with MEN2A are thought to have a de novo mutation in the RET gene.

How is MEN2 diagnosed?

FMTC is suspected in families with two or more cases of medullary thyroid cancer and no evidence of parathyroid or adrenal gland problems.

MEN2A is suspected when there are at least two of the three common tumors (medullary thyroid cancer, pheochromocytoma, or parathyroid adenoma) in one person or close relatives. Close relatives are generally considered to be parents, siblings, and children. Medullary thyroid carcinoma has been reported in children as young as 2 years of age although it more commonly develops between the ages of 8 and 18 years.

MEN2B is suspected in children with mucosal neuromas (lumps on the tip of the tongue) and typical facial features (thickened lips) of a person with MEN2B. Medullary thyroid cancer can occur very early in childhood.

Genetic testing for mutations in the RET gene is available. It is recommended for people with a family history of FMTC, MEN2A, and MEN2B, and anyone diagnosed with medullary thyroid cancer. Mutations in the RET gene are found in more than 95% of families with MEN2A or MEN2B, and in more than 85% of families with FMTC. 

What are the estimated cancer risks associated with MEN2?

The risk of medullary thyroid cancer in people with MEN2 is nearly 100% for all subtypes.

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