Multiple endocrine neoplasia type 2B (MEN2B) is a condition that involves medullary cancer, pheochromocytoma, or neuromas caused by a mutation in the CDKN1B gene. The gene mutation occurs spontaneously and is not inherited.
Characteristics of MEN2A
There are three types of multiple endocrine neoplasias: type 1 (MEN1), type 2A (MEN2A), and type 2B (MEN 2B). The defining characteristic of MEN2B is a mutation in the CDKN1B gene. Unlike the other types of multiple endocrine neoplasias, this type is not caused by an inherited gene mutation and, instead, it occurs spontaneously.
Patients with MEN2B may also be affected my mucosal neuromas and Marfanoid habitus, which is not associated with MEN2A. The prognosis for patients with MEN2B is typically worse than that for patients with MEN 2A, due to more aggressive medullary thyroid cancer (MTC).
Patients with MEN2A usually develop symptoms at an early age, particularly in comparison to other types of multiple endocrine neoplasias. Infants as young as 2 months old have been identified with MTC associated with MEN2B.
Typical symptoms of the condition may include:
- Medullary thyroid cancer
- Pheochromocytoma (e.g. benign tumor of the adrenal glands)
- Neuroma, appearing like bumps on the lips, tongue, mouth, and eyelids
- Muscle, joint, and spinal difficulties
- Digestive symptoms such as constipation or diarrhea
- Excessive sweating
- Itchy skin
- Lump at the base of the neck
Tests that may be used in the diagnostic process for MEN2B include:
- 24-hour urine collection test to detect elevated levels of catecholamines and metabolites (e.g. vanillyl-mandelic acid) in the urine.
- Magnetic resonance imaging (MRI) of the abdomen to detect changes
- Metaiodobenzylguanidine (MIBG) scan to investigate the location of phaeochromocytomas.
- Blood tests to monitor for elevated levels of calcium, parathyroid hormone and calcitonin in the plasma, which an accurate marker for MTC.
- Ultrasound imaging to investigate presence of thyroid tumors.
- Fine-needing aspiration to investigate nature of thyroid tumors.
The main aim of treatment for patients with MEN2B is to increase quantity and quality of life for affected individuals.
This is usually done with a prophylactic thyroidectomy or regular screening for MTC, phaechromocytoma and parathyroid disease, before the development of symptoms. Due to the high risk of developing MTC, removal of the thyroid gland a prophylactic method is often indicated.
For patients with distant metastases, such as in the lungs or liver, at the time of diagnosis, a more complex treatment regime is needed. Most patients will have some involvement of the local lymph nodes and dissection of a central lymph node it, therefore, recommended.
After the removal of the thyroid gland and the tumor, follow-up appointments are important for monitoring the return of the tumor or a new growth. Plasma calcitonin and CEA are important makers in the monitoring of patients for the development of MTC.
The prognosis for patients with MEN2B is typically poorer than that for patients with other types of multiple endocrine neoplasias. This is because MTC associated with this type is usually more aggressive. In these cases, death before the age of thirty years is common with the current treatment methods. Further research is needed to improve this prognosis.