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Multiple endocrine neoplastic syndrome type IIB
Last reviewed: 07.07.2025
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Multiple endocrine neoplastic syndrome, type IIB (MEN IIB, MEN IIB syndrome, mucous neuroma syndrome, multiple endocrine adenomatosis) is characterized by multiple mucous neuromas, medullary thyroid carcinomas, pheochromocytomas, and often Marfan syndrome. The clinical picture depends on the glandular elements involved. Diagnosis and treatment are similar to those of MEN MA syndrome.
About 50% of cases are sporadic rather than related, although the cause of sporadic MEN IIB is unknown. The incidence in men is twice as high as in women. Hyperparathyroidism occurs in cases of MEN IIB. Genetic studies have identified mutations in the receptor tyrosine kinase of oncogenes.
Symptoms of MEN type IIB
Symptoms and signs reflect glandular pathologies. About 50% of patients have the complete mucous neuroma syndrome, pheochromocytoma, and medullary thyroid carcinoma. Less than 10% have only neuromas and pheochromocytomas, while the remaining patients have neuromas and medullary thyroid carcinoma without pheochromocytoma.
Mucous neuromas are often an early sign of the disease and are present in most or all patients. Neuromas appear as small shiny bumps on the lips, tongue, cheeks, and mucous membranes. Neuromas may also appear on the eyelids, conjunctiva, and cornea. Thickened eyelids and diffusely hypertrophied lips are characteristic features. Gastrointestinal motility abnormalities (constipation, diarrhea, and sometimes megacolon) are common and result from diffuse intestinal ganglioneuromatosis. Patients may have Marfan syndrome; skeletal abnormalities of the spine (lordosis, kyphosis, scoliosis), pes cavus, and equinovarus deformity of the feet are common features of the disease.
Medullary thyroid carcinoma and pheochromocytoma resemble the corresponding pathologies of MEN IIA, both being bilateral and multicentric. However, medullary thyroid carcinoma tends to be particularly aggressive in MEN IIB and may affect young children.
Although neuromas, characteristic facial features, and gastrointestinal disturbances are seen early in life, the syndrome may not be recognized until medullary thyroid carcinoma or pheochromocytoma becomes more evident later in life.
Diagnosis of MEN IIB type
MEN IIB syndrome is suspected in patients with a family history of MEN II B, pheochromocytoma, multiple mucous neuromas, or medullary thyroid carcinoma. Genetic testing is highly accurate and is done in first-degree relatives and any relatives with symptoms of the disease.
Pheochromocytoma may be suspected clinically and confirmed by measuring plasma free metanephrines and fractionated urinary catecholamines. Laboratory testing for medullary thyroid carcinoma may be done. MRI or CT is used to look for pheochromocytoma and medullary thyroid carcinoma.
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Treatment of MEN type IIB
Affected patients should have total thyroidectomy immediately after diagnosis. Pheochromocytoma, if present, should be removed before thyroidectomy. In case of gene carriers, prophylactic thyroidectomy in infancy or early childhood is recommended.