Coexisting Reninoma and Aldosterone-Producing Nodule: A Case of Mixed Hyperaldosteronism

Distinguishing primary aldosteronism (PA) from secondary hyperaldosteronism (SH) is traditionally based on reciprocal changes in plasma renin and aldosterone within the renin–angiotensin–aldosterone system. We report a rare "mixed" hyperaldosteronism phenotype in a 41-year-old woman with a 14-year history of refractory hypertension and hypokalemia. Biochemical testing demonstrated extreme plasma renin elevation (1872.00 μIU/mL) and high aldosterone (81.1 ng/dL), which initially suggested SH, but imaging identified the coexistence of a right renal mass and a right endocrine-active adrenal nodule. Following laparoscopic resection of both lesions, histopathology confirmed an atypical juxtaglomerular cell tumor (reninoma) with uncertain malignant potential (Ki-67 index 8%–10%) and an aldosterone-producing nodule (APN). Postoperatively, plasma renin normalized and refractory hypertension resolved without antihypertensive medication. The aldosterone secretion is considered to originate from both the autonomous APN that bypass normal RAAS regulation, and responsive non-neoplastic (zona glomerulosa) cells stimulated by chronic RAAS activation from the reninoma. This rare case of coexisting atypical reninoma and APN highlights the limitations of relying solely on renin–aldosterone patterns and emphasizes that comprehensive multi-modal imaging and endocrine evaluation are necessary to resolve diagnostic paradoxes in complex secondary hypertension.