A 14-year-old boy presents with a neck mass, mucosal neuromas on the lips and tongue, marfanoid habitus with long limbs and high-arched palate, and episodic hypertension with palpitations. His father died of medullary thyroid carcinoma at age 28. Serum calcitonin is markedly elevated at 1200 pg/mL, and 24-hour urinary metanephrines are 4× the upper limit of normal. MRI confirms bilateral pheochromocytoma. Genetic testing reveals the mutation shown in the karyotype marked **A** in the diagram. Which of the following is the MOST APPROPRIATE immediate management step for this patient?
A. Prophylactic total thyroidectomy under general anesthesia
B. Plasma free metanephrine screening and annual calcitonin surveillance only
C. Initiation of levothyroxine replacement therapy
D. Bilateral adrenalectomy or pheochromocytoma resection first, followed by thyroidectomy
Explanation
Why bilateral adrenalectomy or pheochromocytoma resection first, followed by thyroidectomy is right
The patient carries the RET M918T mutation (marked A), which is pathognomonic for MEN2B and is associated with bilateral pheochromocytoma in ~50% of cases. The clinical anchor is that pheochromocytoma MUST BE RESECTED FIRST before any thyroid surgery to prevent intraoperative hypertensive crisis. The markedly elevated 24-hour urinary metanephrines (4× upper limit) and bilateral pheochromocytoma on imaging confirm active catecholamine excess. Resection of the pheochromocytoma(s) must precede thyroidectomy, even though prophylactic thyroidectomy is indicated in M918T carriers before age 1 (or urgently in older children). Once pheochromocytoma is controlled, thyroidectomy can proceed safely (Harrison's 21e, MEN syndromes).
Why each distractor is wrong
Prophylactic total thyroidectomy under general anesthesia: While prophylactic thyroidectomy is indeed mandated in M918T carriers, performing it FIRST in the presence of uncontrolled bilateral pheochromocytoma risks severe intraoperative hypertensive crisis, arrhythmia, and myocardial infarction. The pheochromocytoma must be addressed first.
Initiation of levothyroxine replacement therapy: Levothyroxine is given AFTER thyroidectomy for lifelong replacement, not as an immediate management step. It does not address the acute life-threatening pheochromocytoma.
Plasma free metanephrine screening and annual calcitonin surveillance only: This is a surveillance strategy for at-risk relatives or asymptomatic carriers. This patient has symptomatic, biochemically confirmed bilateral pheochromocytoma and requires definitive surgical resection, not observation.
High-YieldNEET PG
In MEN2B (RET M918T), always resect pheochromocytoma BEFORE thyroid surgery to prevent catecholamine storm.
Harrison's 21e — MEN syndromes
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