NORD gratefully acknowledges Maria Luisa Brandi, MD, PhD, Director, Regional Center for Hereditary Endocrine Tumors, University of Florence, Florence, Italy, for assistance in the preparation of this report.
Multiple endocrine neoplasia type 2 (MEN2) is a rare genetic polyglandular cancer syndrome, characterized by the 100% prevalence of medullary thyroid carcinoma (MTC) and an increased risk of develop other specific tumors affecting additional glands of the endocrine system. The endocrine system is the network of glands that secrete hormones into the bloodstream to reach distant target tissues and organs within the body. Hormones are active molecules, which through their binding to specific receptors in the target cells, regulate the chemical processes (metabolism) that influence vital processes and functions of various organs, including regulating heart rate, body temperature and blood pressure.
MEN2 endocrine tumors may secrete excessive amounts of hormones into the bloodstream, which can result in a variety of symptoms.
This syndrome includes two main clinical subtypes, characterized by different clinical characteristics (phenotype):
MEN2A (accounting for 95% of all MEN2 cases); characterized by the uniform presence of MTC in association with pheocromocytoma (PHEO) or primary hyperthyroidism (PHPT) or both in some patients.
MEN2B (accounting for less than 5% of all MEN2 cases); characterized by a 100% prevalence of an earlier onset and more severe MTC, PHEO but not PHPT.
MEN2A includes four subvariants:
The total prevalence of all MEN2A and MEN2B variants is approximately 1/35,000.
MEN2 can run in families (familial cases) or can occur as the result of a spontaneous genetic change (i.e., new mutation) that occurs randomly for no apparent reason at embryo level.
The onset, progression, and specific symptoms of each case of MEN2 can vary, even among members of the same family. Some individuals may only develop mild symptoms; others may develop serious, life-threatening complications. Some individuals may develop symptoms during infancy or early childhood; others may not develop symptoms until adolescence or young adulthood. Some cases of MEN2 may not become apparent until later during adulthood.
Nearly all individuals with MEN2 develop medullary thyroid carcinoma (MTC), usually very early in life. Additional symptoms vary depending upon the specific subtype of the syndrome. It is important to note that individual cases are highly variable and that not all the affected individuals will develop all of the symptoms discussed below.
Three are the endocrine glands most often affected in MEN2 syndrome: the thyroid, the adrenal glands and, only in the MEN2A variants, the parathyroids.
The thyroid is a small, butterfly-shaped gland located in the front of the neck. The thyroid absorbs iodine (a substance found in many foods) from the blood. The thyroid converts iodine into thyroid hormones, which are essential to regulate the chemical processes (metabolism) of virtually every cell in the body.
The adrenal glands are located on top of the kidneys and produce two hormones called epinephrine and norepinephrine. Other hormones produced by the adrenal glands help to regulate the fluid and electrolyte balance in the body.
The parathyroid glands are four very small glands (approximately the size of a pea) located in the neck that secrete parathyroid hormone (PTH), the principal regulator of calcium homeostasis and serum calcium level.
Multiple Endocrine Neoplasia Type 2A
The first clinical manifestation in MEN2A is, in the majority of cases, is the MTC. Some individuals may have overgrowth (hyperplasia) of thyroid cells (C-cell hyperplasia), a condition that is a benign process, but is considered a precursor to the development of MTC. Nearly all individuals with MEN2A develop C-cell hyperplasia or MTC at some point during their lives. Signs of MTC can be seen early during childhood. If MTC is not detected and treated during childhood, most individuals will develop a mass in the neck or pain in the neck between 15 to 20 years of age.
Approximately 50 percent of individuals with MEN2A will develop a PHEO, a usually benign tumor of the adrenal glands; in many cases of MEN2 both the adrenal glands are affected (bilateral PHEO). In rare MEN2A cases, PHEO can manifest as first clinical sign of the syndrome; the first symptom of a PHEO is usually high blood pressure not responding to pharmacological therapy (intractable hypertension). Other associated symptoms can be headache, palpitations, nervousness, and tachycardia. PHEO is almost always benign (noncancerous), but in approximately 4% of MEN2A patients malignant transformation can occur.
Approximately 20-30% of MEN2A cases have PHPT due to overgrowth (hyperplasia) of parathyroid tissue or development of a benign tumor in the parathyroid glands (adenoma); one to four glands can be affected during lifetime. MEN2A PHPT is usually mild and asymptomatic. Symptoms, due to hypercalcemia, can be depression, muscle weakness and fatigue.
In addition to the classical MEN2A, there are other two, extremely rare, variants which show additional specific symptoms.
One variant of MEN2A is associated with cutaneous lichen amyloidosis (CLA), a condition in which a scaly, itchy skin rash develops due to the accumulation of certain proteins (amyloids) in the skin. These dermatological lesions are particularly evident in the scapular region of the back and have as classical symptom an intense pruritus that improves with sun exposure and worsens during periods of stress. In some cases, the CLA may be present at a young age and manifest prior to the onset of clinically evident MTC, thus serving as a sign for an early diagnosis of the syndrome.
The second variant of MEN2A is associated with Hirschsprung disease, a gastrointestinal condition characterized by absence of certain nerve cell bodies (ganglia) in the smooth muscle wall within a region of the large intestine (i.e., colon). As a result, there is absence or impairment of the involuntary, rhythmic contractions that propel food through the GI tract (peristalsis). Symptoms of Hirschsprung disease include constipation, vomiting, loss of appetite, bloating or swelling (distention) of the abdomen, abnormal accumulation of feces within the colon, and widening of the colon above the affected segment (megacolon). Hirschsprung disease can eventually cause diarrhea, dehydration, and failure to grow and gain weight at the expected rate (failure to thrive).
Multiple Endocrine Neoplasia Type 2B
The MEN2B subtype accounts for about 5% all cases of MEN2. MEN2B was formerly called MEN type 3 (MEN3); currently MEN2B is considered a clinically more aggressive variant of MEN2. Associated symptoms can vary greatly from one person to another. Some symptoms can be very subtle in certain cases.
MTC usually occurs earlier in MEN2B than in MEN2A and is usually more aggressive. A neck mass may be detectable during childhood. Most affected children receive a thyroidectomy (surgical removal of the thyroid) at an early age because MTC can potentially spread (metastasize) at a very early age. In presence of certain specific RET variation, associated to a particularly aggressive form of MTC, a prophylactic thyroidectomy is suggested during the first year of age.
PHEO occurs in approximately 50% of cases of MEN2B (50% of them being bilateral PHEO), with no differences in occurrence and clinical presentation from individuals with MEN2A.
PHPT is absent in MEN2B.
Individuals with MEN2B also have additional symptoms not present in all the MEN2A subtypes.
MEN2B can be associated with development, during infancy or early childhood, of multiple, benign tumors, called neuromas, arising from certain nerve cells. MEN2B neuromas usually affect the mucous membranes (mucosa) lining the surface of the tongue, lips, the roof of the mouth (palate), eyelids, voice box (larynx), pharynx and nasal passages. The conjunctiva, the thin, clear membrane that covers the whites of the eyes, may also be affected. The presence of multiple neuromas can cause affected areas to appear swollen such as the lips, which often appear full and prominent. Infants and children with MEN2B may have additional distinctive facial features including eyelids that are flared forwarded (anteverted), broad-based nose, a wide-expression, and a coarse, elongated facial appearance. These distinctive facial features are not always present.
In MEN2B, benign growths arising from nerve cells called ganglion cells may also occur (ganglioneuromatosis). These growths occur in the gastrointestinal tract and may cause swelling (distention) of the abdomen, diarrhea, constipation, and an abnormally enlarged colon (megacolon). Affected infants often fail to gain weight and grow at the expected rate for age and sex (failure to thrive).
Some individuals with MEN2B may develop additional symptoms including a sunken breastbone (pectus excavatum), lax or loose joints, abnormal curvature of the spine, muscle weakness, and a “marfanoid habitus”, a condition in which affected individuals tend to be thin with unusually tall stature; long, slender fingers and toes (arachnodactyly); and elongated arms and legs. The term “marfanoid” refers to Marfan syndrome, a distinct genetic disorder in which these findings are characteristic. MEN2B is unrelated to Marfan syndrome other than sharing some similarities in build.
Familial Medullary Thyroid Carcinoma
By definition, familial medullary thyroid carcinoma (FMTC) must occur in at least four members of a family in the absence of additional signs and symptoms MEN2A or MEN2B such as PHEO or parathyroid adenoma. MTC is less aggressive in this variant than other MEN2A variants and MEN2B familial form then when it is associated with MEN types 2A or 2B. Onset is usually during adulthood. FMTC is now considered a variant of MEN2A with a partial clinical penetrance.
Medullary Thyroid Carcinoma
Medullary thyroid carcinoma (MTC) is a form of cancer that arises from certain cells within the thyroid called C cells (parafollicular cells). This type of cell produces the hormone calcitonin, which helps to regulate calcium metabolism. MTC is an aggressive form of cancer and may spread via the lymph nodes or bloodstream to affect other organs. The first sign of MTC is often a firm mass in the thyroid or abnormal enlargement of nearby lymph nodes (lymphadenopathy). An MTC mass in the neck may be painful. MTC can spread (metastasize) to other areas of the body. Because MTC can be cured by surgical removal of the thyroid, prompt diagnosis of this condition is essential to prevent the cancer from spreading. Individuals with MTC that progresses to cause a large tumor or that spreads to other areas of the body may develop chronic diarrhea as a result of the overproduction of calcitonin. If MTC spreads, it may cause abdominal pain, jaundice and in rare cases bone pain or tenderness.
Pheochromocytoma (PHEO) is a rare type of tumor that arises from certain cells known as chromaffin cells, which produce hormones necessary for the body to function properly. PHEO produce norepinephrine and epinephrine, hormones that are involved with the sympathetic nervous system, which controls various involuntary activities in the body such as raising blood pressure or regulating the heartbeat. Most PHEOs originate in one of the two adrenal glands located above the kidneys. Most chromaffin cells are found in the adrenal gland’s inner layer, which is known as the adrenal medulla.
Symptoms associated with PHEO include high blood pressure (hypertension), chronic headaches, excessive sweating, and/or heart palpitations. Nervousness, anxiety, and loss of color (blanching) of the skin may also occur. High blood pressure associated with PHEO often does not respond to therapy (intractable hypertension).
In some cases, an undetected PHEO can potentially cause life-threatening complications such as hypertensive crisis when undergoing procedures requiring anesthesia. Hypertensive crisis is a severe increase in blood pressure that can damage blood vessels and lead to a stroke. However, because of better diagnosis, recognition, and therapies regarding PHEO, such life-threatening complications are rare in individuals with MEN2 who develop PHEO.
The parathyroid glands are four very small glands (approximately the size of a pea) located in the neck that secrete PTH, the main hormonal regulator of calcium homeostasis and serum calcium level. Hyperparathyroidism is a clinical condition indicating a prolonged high level of circulating PTH, which can be associated to hypercalcemia.
Hyperparathyroidism can be very mild and may not cause any obvious symptoms (asymptomatic), or, conversely, it can result in persistent elevated serum level of calcium (hypercalcemia), which can eventually cause kidney stones or damage the kidneys or be responsible for bone demineralization (osteoporosis) and increased risk of fragility fractures. Hyperparathyroidism-derived hypercalcemia can cause additional symptoms including fatigue, weakness, constipation, nausea, ulcers, indigestion, high blood pressure (hypertension), and muscle or bone pain. Central nervous system abnormalities can eventually develop including mental status changes, lethargy, depression, and confusion. Most individuals with hyperparathyroidism do not develop all of these symptoms, especially when the condition is diagnosed early.
MEN2 is caused by a change (mutation) of the RET gene. The RET gene is an oncogene, a gene that plays a role in the development of cancer.
When operating normally, the RET protein produced by the RET gene exerts several key functions including control of cell division and regulation of cell death (apoptosis). Activating mutations of the RET gene lead to uncontrolled growth of cells, causing tumor formation in target organs.
MEN2 is a dominant genetic disorder. A single copy of a mutated RET gene is sufficient for the appearance of the disease. The RET mutation may be inherited from one of the parents, or occur as a spontaneous genetic change (new mutation) that occurs randomly for no apparent reason at embryo level. The risk of passing the abnormal gene from affected parent to offspring is 50 percent for each pregnancy, with equal risk for male and female children.
No somatic mutations of the second copy of the RET gene have been reported or necessary for the development of tumors (as for MEN1 syndrome).
Specific RET mutations drive the clinical presentation of the disease (genotype-phenotype correlation) and the identification of the mutation in patients can direct the therapeutic approaches for both MTC and PHEO, and the diagnostic plan for PHPT.
MEN2 affects males and females in equal numbers. It has been estimated to affect 1 in 35,000 people in the general population. Some researchers believe that many cases of MEN2 go undiagnosed or misdiagnosed, making it difficult to determine the disorder’s true frequency in the general population. MEN2A is the most common subtype accounting for about 95% of all cases. MEN2B accounts only 5% of cases. All cases of MTC (i.e. including both those associated with MEN2 and those arising at sporadic tumors) account for approximately 5-10% of all thyroid cancers.
Affected individuals may receive a clinical diagnosis of MEN2 following a specific clinical evaluation for MEN2-associated tumors, a detailed patient and familial history and the identification of characteristic features. The characteristic features of MEN2A are the presence of two or more specific endocrine tumors (i.e., MTC, PHEO, and parathyroid hyperplasia or adenoma). Diagnostic features of MEN2B include the identification of MTC, PHEO, multiple neuromas, distinctive facial features, and a “marfanoid” habitus. FMTC is diagnosed in individuals with only MTC in at least four family members without the presence of other symptoms associated with MEN2A or MEN2B.
A variety of tests can aid in the diagnosis of MEN2. Such tests include those designed to detect elevated levels of certain hormones in the blood. Identification of elevated hormones in the blood can be an indication of specific endocrine tumors. For example, identification of elevated levels of calcitonin can indicate the presence of MTC, elevated levels of PTH can indicate the presence of a parathyroid tumor, and elevated levels of catecholamines may indicate the presence of an active PHEO. A variety of imaging (x-ray) scans may also be performed to aid in identifying the size and specific location of tumors, and lead surgical interventions.
The clinical diagnosis of MEN2 can be confirmed by genetic diagnosis through molecular genetic testing identifying a missense mutation of the RET gene.
The treatment of MEN2 may require the coordinated efforts of a team of specialists. Endocrinologists, surgeons, cancer specialists (oncologists), and other healthcare professionals may need to systematically and comprehensively plan an affect child’s treatment. Treatment is directed toward the specific symptoms that are apparent in each individual and may include surgical removal of tumors and drugs to counteract the effects of excess hormones or replacement of hormones no longer produced by the body (i.e., following surgical removal of a gland).
Specific therapeutic procedures and interventions may vary depending upon numerous factors, such as the specific subtype present, whether C-cell hyperplasia or cancer has developed; the size and type of tumors; the severity of symptoms due to excess hormone production; whether malignant cancer is already present and whether it has spread to lymph nodes or distant sites; an individual’s age and general health; and/or other elements. Decisions concerning the use of particular interventions should be made by physicians and other members of the healthcare team in careful consultation with the patient, based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks; patient preference; and other appropriate factors.
Because of advancements made in the recognition, genetics (i.e., identifying the mutated gene), and treatment of MEN2, certain serious, life-threatening complications associated with the disorder such as the spread (metastasis) of MTC or rare complications of a PHEO have been greatly reduced. The result of the genetic test can drive the therapeutic approaches for both MTC and PHEO.
The standard therapy for individuals with MEN2 is surgical removal of the thyroid, a procedure called a thyroidectomy. Surgical removal of the thyroid is often performed as a preventive measure, even if cancer or C-cell hyperplasia has not developed yet. Individuals will require life-long hormone replacement therapy of the hormones normally produced by the thyroid. The age of thyroidectomy performance may vary depending upon the specific MEN2 subtype and the specific RET mutation. The recommendations on the timing of prophylactic total thyroidectomy and extent of surgery are classified, accordingly to the American Thyroid Association (ATA), into three risk levels (highest risk, high risk, and moderate risk), based on the specific RET gene mutation:
In all three cases, a life-long thyroid hormone supplementation is needed after thyroid removal.
Thyroidectomy can potentially cause the partial or complete ablation of the parathyroid glands causing severe reduction/absence of PTH (hypoparathyroidism). The ability of surgeon is important in identifying parathyroid glands and preserving them to be re-implanted (autotransplant) into the non-dominant forearm, reducing/avoiding the risk of post-operatory hypoparathyroidism. Post-operatory hypoparathyroidism requires life-long treatment with calcium and vitamin D analogues.
MEN2A PHPT is usually mild and it can be controlled by medical therapy with calcimimetics or, more frequently, by the surgical removal of the parathyroid gland followed by the re-implantation of some healthy parathyroid tissue into the arm. Because there is a risk of a benign tumor recurring in the healthy parathyroid tissue, transplanting that tissue into the arm would spare affected individuals from being operated on in the same area (i.e., the neck).
Surgery is the main form of therapy for individuals with PHEO. Surgical removal of one or both of the adrenal glands is often performed. Both adrenal glands are often removed even in individuals with a PHEO affecting only one gland (unilateral) because of the high risk of the other adrenal gland becoming affected later on. The most common surgical procedure for treating PHEO is laparoscopic laparotomy. During this procedure, a small incision is made in the abdomen, a small tube is inserted (laparoscope) through the incision, and the tumor is removed. Before surgery, some affected individuals may need to be treated with alpha-adrenergic blockers and beta-adrenergic blockers to minimize the effects of adrenal hormones. Alpha-adrenergic blockers such as phenoxybenzamine are used to control hypertension. In some cases, beta-adrenergic blockers such as propranolol can also be used to treat hypertension.
In cases where MTC has spread or where malignant transformation of a PHEO has occurred chemotherapy or radiation therapy may be used.
Before any surgery for individuals with MEN2, screening for the presence of an active PHEO should be performed because of the risk of anesthesia-induced hypertensive crisis.
The U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) approved two orally administered thyrosin kinase inhibitors (TKIs), Caprelsa (vandetanib) in 2011 and Cabometyx (cabozantinib) in 2012, for the treatment of patients with advanced progressive MTC.
Genetic counseling is recommended for affected individuals and their families.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov . All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:https://rarediseases.org/for-patients-and-families/information-resources/news-patient-recruitment/
For information about clinical trials sponsored by private sources, contact:www.centerwatch.com
For more information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder.
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