BACKGROUND: Primary aldosteronism (PA) is a syndrome which includes a group of clinical entities in which aldosterone production is inappropriately high and nonsupressible by sodium loading. The most frequent causes of PA are adrenal adenoma and unilateral or bilateral primary hyperplasia.METHODS: We report a case of a 55-year-old man with a 10-year history of hypertension in whom functional hormonal studies were indicative of PA. Because adrenal venus sampling was not available at our hospital, the investigation was conducted with a computed tomography (CT) scan and a scan with 131-iodocholesterol (NP-59) which both revealed a left adrenal adenoma.RESULTS: The tumor was excised laparoscopically without any complications and the histological findings confirmed the diagnosis of an aldosterone-producing adenoma. Blood pressure remained normal despite the discontinuation of antihypertensive drugs, further supporting that the adrenal tumor was indeed the cause of high blood pressure. Unfortunately, blood pressure began to rise again 2 months later, and laboratory findings indicated the presence of PA once again. Spironolactone was instituted and blood pressure significantly improved and was finally controlled by the addition of amlodipine.CONCLUSION: We report this case to underline the difficulties in the discrimination between adenoma and hyperplasia in everyday clinical practice. Although the CT and scintigraphic findings strongly pointed toward an adenoma, the fact that PA re-appeared shortly after the operation, indicated that the underlying cause of the PA was hyperplasia and not adenoma after all.