Metachronous Bilateral Adrenal Adenomas Causing Adrenocorticotropic Hormone-Independent Cushing's Syndrome: A Case Report.

Bilateral adrenal adenomas (BAAs) represent an uncommon etiology of adrenocorticotropic hormone (ACTH)-independent Cushing's syndrome (CS); however, metachronous BAAs, where the adenomas present years apart, are exceptionally rare, with only a few cases previously reported. We present the case of a 53-year-old woman who developed ACTH-independent CS from a left adrenal cortical adenoma 19 years ago, treated successfully with a left-sided adrenalectomy. Nineteen years after the first episode, she presented with classic hypercortisolism symptoms, including central obesity, striae, and osteoporosis. Workup confirmed recurrent ACTH-independent CS with a low baseline ACTH level and a failure of both low- and high-dose dexamethasone suppression tests to suppress cortisol. Laparoscopic-assisted right-sided adrenalectomy was performed after image confirmation. Adrenal cortical adenoma was diagnosed by histological examination. Following the adrenalectomy, the patient required permanent glucocorticoid and mineralocorticoid replacement therapy. Serial brain magnetic resonance imaging (MRI) scans were initiated for Nelson's syndrome (NS) surveillance. Over 38 months of follow-up, the patient's clinical symptoms improved, and no signs of NS were noted. This case represents the longest detailed reported case with an interval of 19 years between the diagnosis and surgical treatment of metachronous BAAs causing ACTH-independent CS. This rarity highlights the critical importance of long-term and regular follow-up for patients with unilateral adrenal adenoma to monitor for subsequent contralateral masses.