Recurrent Cushing Syndrome From Metastatic Adrenocortical Carcinoma With Fumarate Hydratase Allelic Variant

BACKGROUND: Adrenal Cushing syndrome (CS) is usually benign in etiology; however, although rarely, it can be due to adrenocortical carcinoma (ACC); in which case, diagnosis and management are quite complicated. CASE REPORT: A 34-year-old woman presented with worsening confusion, weight gain, new-onset diabetes, and hypertension. Her history was significant for a 7.4-cm left adrenal mass and CS, which were treated with left adrenalectomy 2 years ago. She received hydrocortisone replacement therapy after the surgery, which was discontinued on admission when evaluation showed hypokalemia, hypercortisolemia, and undetectable adrenocorticotropic hormone. Subsequent testing included 1-mg and 8-mg dexamethasone suppression tests, which did not suppress cortisol; late-night salivary cortisol measurement, which yielded a very high salivary cortisol level; and 24-hour urinary cortisol measurement. The level of 11-deoxycortisol was elevated. A computed tomography scan revealed multiple hepatic lesions, which were fluorodeoxyglucose avid, and a biopsy confirmed metastatic ACC. She received treatment with mitotane, metyrapone (later changed to mifepristone), doxorubicin, cisplatin, and etoposide. Over 8 weeks, mitotane levels became therapeutic at 20 mcg/mL, the hepatic masses decreased in size, and she transitioned to adrenal insufficiency and improved glycemic control. Next-generation sequencing of liver biopsy and germline testing revealed a frameshift loss-of-function allelic variant in the FH gene that encodes the protein fumarate hydratase. DISCUSSION: We report a case of recurrent CS due to metastatic ACC in a patient with a previously resected adrenal adenoma and FH allelic variant. CONCLUSION: Metastatic ACC presenting with severe CS presents a diagnostic and management challenge where combination therapy guided by a multidisciplinary team is essential. FH allelic variant may contribute to ACC progression.