SUN-502 - A Rare Diagnosis: FH-Associated Pheochromocytoma with Aldosterone-Secreting Micronodules in the Ipsilateral Adrenal Gland

Background:
Adrenal disorders are a common cause of resistant hypertension. Pheochromocytomas (Pheo) are rare neuroendocrine tumors occurring in 0.3–0.6% of hypertensive patients, whereas primary aldosteronism (PA) is more common, affecting 5-14%. The coexistence of Pheo and PA is exceedingly rare because they originate from distinct adrenal cell types—chromaffin cells of the medulla and adrenocortical cells, respectively.

Case Presentation:
A 66-year-old woman presented with dizziness, palpitations, diaphoresis, and uncontrolled hypertension (170/90 mmHg), while taking amlodipine, valsartan–hydrochlorothiazide, and metoprolol. Laboratory evaluation showed elevated plasma normetanephrine (3.6 nmol/L; ref < 0.89), suppressed renin ( < 0.1 ng/mL/hr), plasma aldosterone 13.1 ng/dL (ARR 131) and a potassium of 4.0 (ref 3.5-5.0 mmol/L). Non-contrast abdominal CT revealed a 2.0 × 2.3 cm right adrenal nodule.

Right adrenalectomy revealed a 2.8 cm Pheo and aldosterone synthase immunostaining identified aldosterone-producing micronodules. Three days postoperatively, normetanephrines decreased to 1.15 nmol/L, PRA remained suppressed, aldosterone improved to 6.1 ng/dL, and blood pressure normalized (120/60 mmHg) on valsartan monotherapy.

Germline genetic testing identified a likely pathogenic FH gene variant (c.580G>A, p.A194T), associated with Pheo and paraganglioma. One year later, blood pressure rose to 155/87 mmHg with persistently suppressed renin and PAC 13.7 ng/dL. Plasma metanephrines were normal. CT showed no recurrence. Spironolactone achieved blood pressure of 128/72 mmHg and normalized renin; she remains normotensive on monotherapy.

Conclusion:
This case highlights the rare coexistence of pheochromocytoma and aldosterone-producing micronodules within the same adrenal gland. It underscores the importance of comprehensive evaluation for secondary hypertension, postoperative biochemical monitoring, and long-term surveillance. While the patient has a likely pathogenic FH variant, any connection to the coexistence of these adrenal pathologies is uncertain.

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