Bilateral Pheochromocytoma in a Patient With MYC-Associated Protein X ( MAX) Genetic Predisposition

Pheochromocytoma and paraganglioma (PPGL) are associated with a genetic predisposition in at least 40% of patients and likely 100% when presenting with bilateral or multifocal PPGL. Most patients with bilateral pheochromocytomas will prove to have neurofibromatosis type 1, multiple endocrine neoplasia type 2, or von Hippel-Lindau disease. Bilateral pheochromocytoma associated with the loss of function in the MAX (MYC-associated factor X) gene represents 1.7% of cases.

Case Report

The patient was a 56-year-old man who presented for evaluation of incidentally discovered bilateral adrenal tumors during computed tomography (CT) of chest performed for lung cancer screening. Subsequent abdominal CT demonstrated a 2.8-cm left adrenal mass with an unenhanced CT attenuation of 38 Hounsfield units (HU) and a 3.5-cm right adrenal mass with an unenhanced CT attenuation of 27 HU ( Fig. 42.1 ) . Hormonal workup demonstrated catecholamine excess ( Table 42.1 ). Medical history included diabetes mellitus type 2 and hypertension of 5 years, duration. His medication regimen included six antihypertensive medications (amlodipine, benazepril, carvedilol, clonidine, hydrochlorothiazide, and doxazosin) and glyburide and metformin for diabetes mellitus. His blood pressure was 126/83 mmHg, heart rate 72 beats per minute, and body mass index 30.9 kg/m ² . Family history was positive for a metastatic pheochromocytoma in his sister, who died of complications from PPGL. His sister did undergo germline mutation testing, which was unrevealing.

TABLE 42.1

Laboratory Tests

Biochemical Test	Result	Reference Range
Plasma metanephrine, nmol/L	0.3	<0.5
Plasma normetanephrine, nmol/L	17	<0.9
24-Hour urine:
Metanephrine, mcg	259	<400
Normetanephrine, mcg	4882	<900