8563 Pheochromocytoma Screening In A Patient With Neurofibromatosis Type I And Medication-Resistant Hypertension

Abstract Disclosure: E. Mora: None. A. Bolduc, MD: None. G. Elshimy: None. Title: Pheochromocytoma Screening in a Patient With Neurofibromatosis Type I and Medication-Resistant Hypertension Background: Patients with neurofibromatosis type I (NF1) have a higher risk of pheochromocytoma and it may be missed if no screening done, thus placing the patient at risk of stroke and/or myocardial infarction. The prevalence of pheochromocytoma in patients with NF1 is 2.9% according to a retrospective cohort study by Gruber et al. We present a case of biochemically silent pheochromocytoma in a patient with NF1 and resistant hypertension Clinical case: A 74-year woman with NF1 presented with episodic headaches and labile systolic blood pressure (BP) in the 170-200s mm Hg on three different antihypertensives consistent with pheochromocytoma. Initial tests for renal artery stenosis and pheochromocytoma showed normal plasma MN (0.43 nmol/L, n< 0.50 nmol/L) and NM (0.86 nmol/L, n< 0.90 nmol/L), and normal flow in both renal hila by color Doppler and no large suprarenal masses identified on retroperitoneal US. Duplex imaging of the bilateral kidneys showed no evidence of renal artery stenosis. CT of abdomen/pelvis with and without IV contrast showed a 1.6 cm nodule on Right (RT) adrenal gland that measured 36 HU on unenhanced phase with an absolute washout of 67%. No discrete nodule in Lt adrenal gland. Dotatate PET/CT revealed a Rt adrenal nodule with elevated asymmetric activity (measured 28.1 standardized uptake values (SUV), n for liver: max 12.3, spleen: max 23.5) relative to the normal physiologic activity of the Leftt adrenal gland, which is concerning for pheochromocytoma. The patient was then referred to our endocrine clinic for further evaluation 6 months after the initial presentation. Labs showed normal aldosterone (5.8 ng/dL, n≤39.2 ng/dL), cortisol (7.66 mcg/dL, n: 3.09-22.40 mcg/dL), ACTH (20 pg/mL, n: 7.2-63 (AM collection), and DHEA-S (28 mcg/dL, n:5.3-124 mcg/dL). Normal repeat plasma MN (0.38 nmol/L, n< 0.50 nmol/L) and NM (0.46 nmol/L, n< 0.90 nmol/L). Repeat CT adrenal washout redemonstrated 1.4 cm Rt adrenal nodule that measured 39 HU on non- contrast image with an absolute washout of 68%. Patient will have a surgical resection of the Rt adrenal biochemically silent pheochromocytoma next week and she has been receiving an alpha-blocker prior to surgery to decrease risk for labile BP. Discussion and Conclusion: This case illustrates how CT and DOtatate scan findings can alert providers to the presence of a pheochromocytoma, even in biochemically negative patients. We recommend pheochromocytoma screening in all patients with NF1 to prevent delayed diagnosis and complications of untreated pheochromocytoma. Presentation: 6/1/2024