USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What genetic mutation is found in MEN 2b that leads to the development of Medullary thyroid carcinoma, Pheochromocytoma, and mucosal neuromas?

1. MEN 1

2. MEN 2a

3. MEN 2b

4. Pseudopseudohypoparathyroidism

The correct answer is: MEN 2b

The correct answer is C, referring to MEN 2b, which is associated with a specific genetic mutation in the RET proto-oncogene. This mutation is responsible for the development of several conditions, including medullary thyroid carcinoma, pheochromocytoma, and mucosal neuromas, which are characteristic features of MEN 2b. MEN 2b is a rare inherited syndrome that results from mutations in the RET gene, leading to the abnormal growth of certain tissues. The RET gene plays a crucial role in cell signaling and development during embryogenesis. When mutated, it can cause the proliferation of specific cell types, which contributes to the clinical manifestations seen in MEN 2b. Medullary thyroid carcinoma arises from parafollicular C cells of the thyroid, pheochromocytoma originates from adrenal medulla chromaffin cells, and mucosal neuromas are a result of neural crest cell proliferation. The presence of these tumors and lesions is linked directly to the RET mutations seen in MEN 2b, indicating the importance of genetic screening in affected individuals for early detection and management. Other options, such as MEN 1 and MEN 2a, are associated with different genetic mutations and clinical features. MEN 1 is