During screening for hereditary pheochromocytoma syndromes, a 42-year-old woman with a family history of medullary thyroid cancer is found to have a unilateral adrenal mass with elevated catecholamines. What is the most common genetic syndrome associated with pheochromocytoma in this clinical context?

Explanation

## Hereditary Syndromes Associated with Pheochromocytoma **Key Point:** MEN2 is the most common hereditary syndrome associated with pheochromocytoma in the general population, and the presence of medullary thyroid cancer (MTC) is a cardinal clue to MEN2 diagnosis. ### Comparison of Hereditary Pheochromocytoma Syndromes | Syndrome | Gene | Frequency of Pheo | Key Features | MTC Association | | --- | --- | --- | --- | --- | | **MEN2A/2B** | **RET** | **50%** | Medullary thyroid cancer, hyperparathyroidism (2A), mucosal neuromas (2B) | **Yes (100%)** | | NF1 | NF1 | 1–5% | Neurofibromatosis, optic nerve gliomas, café-au-lait spots | No | | VHL | VHL | 10–20% | Hemangioblastomas, renal cysts, RCC, pancreatic cysts | No | | SDH (A, B, D) | SDHA, SDHB, SDHD | 30–40% | Paragangliomas (extra-adrenal), malignancy risk 30–40% | No | **High-Yield:** The **clinical triad of MEN2A** is: 1. Medullary thyroid carcinoma (nearly 100%) 2. Pheochromocytoma (50%) 3. Primary hyperparathyroidism (20–30%) ### Why MEN2 Is the Answer The stem explicitly mentions **medullary thyroid cancer** in the family history. This is the hallmark of MEN2 and is present in virtually all MEN2 patients. The presence of both MTC and pheochromocytoma in a single patient or family is pathognomonic for MEN2. ### Diagnostic Algorithm ```mermaid flowchart TD A[Pheochromocytoma diagnosed]:::outcome --> B{Family history or syndromic features?}:::decision B -->|MTC, hyperparathyroidism| C[MEN2: RET testing]:::action B -->|Neurofibromas, café-au-lait| D[NF1: NF1 gene testing]:::action B -->|Hemangioblastomas, RCC| E[VHL: VHL gene testing]:::action B -->|Extra-adrenal, malignant| F[SDH: SDHA/B/D testing]:::action C --> G[RET mutation confirms MEN2]:::outcome D --> H[NF1 mutation confirms NF1]:::outcome E --> I[VHL mutation confirms VHL]:::outcome F --> J[SDH mutation confirms familial paraganglioma]:::outcome ``` ### Clinical Pearl **MEN2 pheochromocytomas** have distinct features: - Usually **unilateral** (unlike VHL, which has 50% bilateral rate) - Rarely malignant (<5%) - Often diagnosed **after** MTC screening - Require **adrenalectomy before thyroidectomy** to prevent catecholamine surge **Screening strategy in MEN2:** 1. **RET genetic testing** in all suspected MEN2 families 2. **Annual plasma metanephrines** or 24-hour urine metanephrines in RET-positive individuals 3. **Annual calcitonin** for MTC surveillance 4. **Serum calcium and PTH** for hyperparathyroidism [cite:Harrison 21e Ch 397]