FRI369 SDHB Hereditary Pheochromocytoma Paraganglioma Syndrome With Biochemically Silent Pheochromocytoma

Disclosure: A.M. Skariah: None. C.C. Zacharia: None. Background: Paragangliomas are rare neuroendocrine tumors arising from extra-adrenal autonomic paraganglia. Majority of cases are sporadic but 30-50% are associated with genetic mutations. Patients with SDHB mutations can present with pheochromocytoma, paragangliomas or both. Lesions are usually extra-adrenal and typically secrete norepinephrine and occasionally dopamine. These cases are often associated with higher malignancy rates (up to 79%) compared to other SDH-x associated mutation cases. Clinical Case: Our patient is a 64-year-old female with history of secondary adrenal insufficiency, hypothyroidism, osteoporosis, GAD who presented in 2005 with left occipital headache and dysphagia. Workup was notable for a glomus tumor. She underwent tumor embolization, resection, radical neck dissection and radiation therapy. Genetic testing was not performed at the time of diagnosis. Routine biochemical surveillance was done postoperatively. In 2018, the patient was found to have a mild elevation of normetanephrine 248 pg/ml (<148 pg/ml) and total metanephrine 297 pg/ml (<205 pg/ml) levels. Subsequent plasma, urinary metanephrine/catecholamine studies were negative. In 2021, her brother was diagnosed with pheochromocytoma. Genetic testing was then pursued in the patient, and she was found to have a pathogenic mutation c.724C>A (p.R242S) in the SDHB gene. In June 2022, CT chest, abdomen and pelvis with contrast was ordered, and she was found to have a homogeneously enhancing 1.3 x 1.1x 1.4 cm left adrenal nodule with indeterminate imaging characteristics. Following this CT, DOTATATE PET CT scan was done and demonstrated somatostatin avidity in the region of previously resected left glomus jugular tumor, right adrenal gland nodule and left inferior pubic ramus sclerotic lesion. Repeat biochemical testing remained negative for catecholamine excess. Despite being asymptomatic, there was concern for a biochemically silent pheochromocytoma. Alpha blockade was completed prior to right adrenalectomy in November 2022 and surgical pathology confirmed pheochromocytoma. The patient remains clinically stable, and she is now undergoing radiation therapy of her left pubic ramus lesion. Conclusion: It is important to have genetic evaluation early in the workup for a newly diagnosed PPGL. Additionally, suspicion for biochemically silent pheochromocytoma should be present even in the setting of negative biochemical workup and positive SDHB mutation. Presentation: Friday, June 16, 2023