SAT-364 Adrenal Medullary Hyperplasia Mimicking Pheochromocytomas in a Critically Ill Patient with Acute Myeloid Leukemia and Disseminated Intravascular Coagulopathy

Abstract A. Saavedra-Simmons: None. L.A. Marion: None. P.M. Sadow: None. M.A. Blake: None. E.L. Blouch: None. R.A. Hodin: None. L.E. Dichtel: Research Investigator; Self; LED has received research support from Perspectum Ltd. and research support from Lumos Pharma, all per investigator-initiated request, and additional research support from Recordati and NovoNordisk. Other; Self; LED has equity in Marea Therapeutics and is a consultant for Lumos Pharma, LED is a fellow at Third Rock Ventures through the Mass General Brigham’s Innovation Fellows Program, but remains a full-time employee of Mass General Brigham during the course of this educational program (10/1/2022-9/30/2024). Background: Adrenal medullary hyperplasia (AMH) is a rare, benign condition that can present similarly to pheochromocytomas (PCC) clinically, biochemically and radiographically; differentiation requires histopathologic review. We present a case of a critically ill patient with bilateral adrenal masses and elevated catecholamines suspected of having PCC but ultimately diagnosed with AMH. CASE: A 54yo male with newly diagnosed acute myeloid leukemia presented with confusion and was incidentally found to have adrenal nodules measuring up to 2.8 cm (right) and 4.8 cm (left). Calcium was 15.9 mg/dL (8.5-10.5 mg/dL), PTH 312 pg/dL (10-60 pg/mL) and bilateral parathyroid lesions were found on imaging. Plasma normetanephrines (PNM) were 2.9 nmol/L (<0.90 nmol/L); urine normetanephrines (UNMs) were 5957 mcg/24h (<900 mcg/24h). Plasma and urine metanephrines were normal. Importantly, these tests were obtained in the intensive care unit, where the patient had developed disseminated intravascular coagulopathy. There was suspicion for an inherited syndrome given PTH-dependent hypercalcemia, bilateral parathyroid lesions and maternal history of PCC. After recovery from critical illness, bilateral adrenalectomy was performed for diagnostic purposes and medical optimization prior to planned bone marrow transplant. Surgical pathology unexpectedly revealed no adrenal masses and demonstrated only mild thickening of the bilateral adrenal medullas. Histopathology showed no pathological evidence for PCC, adrenal cortical neoplasia or neoplasia of the extra-adrenal paraganglia. Periadrenal fat was sectioned and appeared grossly normal. Postoperative PNM and UNM levels normalized, and there was no evidence of adrenal masses on follow-up CT. On retrospective review, the adrenal lesions on initial imaging were thought to be consistent with marked medullary hyperplasia that nearly halved on 3-week interval imaging, which could be consistent with resolution to mild AMH on pathology 7 weeks after the initial CT. Conclusion: We describe a case of a patient with significantly elevated catecholamine levels, PTH-dependent hypercalcemia with parathyroid lesions and family history of PCC who was incidentally found to have radiologic evidence of bilateral adrenal masses that on pathology demonstrated mild AMH. While there have been reports of similar cases in the literature of AMH appearing as adrenal masses on imaging, no explanation for the discrepancy in imaging and histopathology has been described. Animal studies suggest that the adrenal glands can become enlarged and hypertrophied during an acute stress event, possibly mediated by acute adrenal medullary hypersecretion. We thus hypothesize that AMH can mimic PCC on imaging in critical illness due to increased secretion of ACTH and catecholamines leading to hyperemia and adrenal thickening. AS and LAM contributed equally. Saturday, June 1, 2024