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Multiple endocrine neoplasia type 2A
Multiple endocrine neoplasia 2A (MEN2A) syndrome is a form of MEN2 (see this term) characterized by medullary thyroid carcinoma (MTC; see this term) in combination with pheochromocytoma (see this term) and primary mild hyperparathyroidism resulting from hyperplasia or adenoma of the parathyroid cells.
Prevalence of MEN2A is approximately 1/40,000 and it accounts for about 70-80% of all cases of MEN2.
Disease onset is before 35 years of age (usually between 5 and 25 years), with MTC generally being the first manifestation. Diarrhea is the most frequent systemic symptom. Rare variants of MEN2A can be associated with cutaneous lichen amyloidosis (see this term) or excessive production of ACTH. Patients can also develop disturbances in gut transit that resemble those seen in Hirschsprung disease (HD; see this term) which lead to megacolon and chronic colonic obstruction. Pheochromocytoma is diagnosed at an earlier age and is generally milder. Hyperparathyroidism is mild and may be asymptomatic.
Missense mutations altering the conserved cysteine codons adjacent to the transmembrane domain of the RET proto-oncogene (10q11.2) have been identified in the germline DNA of patients with MEN2A.
Transmission is autosomal dominant.