SUN-501 Paraganglioma presenting with crisis, with subsequent tumor infarction and shrinkage

Abstract Disclosure: C. Choo: None. T. Puar: None. This case report describes a 54-year-old malay male with a left para-aortic paraganglioma presenting in crisis. His past medical history included Diabetes Mellitus Type 2 with recent worsening control, Hypertension and Obstructive Sleep Apnoea (OSA). He had previously elevated urinary and plasma metanephrine in 2019 (1.2-2.1x upper limit normal, ULN), but full-body computed tomography (CT) imaging did not identify any masses. This was attributed to OSA. He presented in July 2024 with abdominal pain, giddiness, and vomiting. He was profoundly hypotensive, requiring aggressive fluid resuscitation. Following the administration of intravenous metoclopramide and morphine, paroxysmal blood pressure trends were observed, with hypertensive episodes. A CT mesenteric angiogram performed to investigate raised lactate and hypotension revealed a 7.2 × 4.9 × 6.2 cm left retroperitoneal mass. Initial plasma metanephrines measured in the High-Dependency Unit were elevated – metanephrine at 6.33 nmol/L [19.1x ULN] and normetanephrine at 3.14 nmol/L [4.42x ULN]. 24-hour urinary metanephrine and normetanephrine were markedly raised at 86 664 nmol/day [57.8x ULN], and 14 298 nmol/day [7.86x ULN] respectively. Serial measurements of plasma and urinary metanephrines during the hospitalization showed a downward trend. Two weeks into the admission, 24-hour urinary metanphrine reduced to 3677 nmol/day [2.45x ULN] whilst normetanephrine was 6503 nmol/day [3.42x ULN]. Given the atypical radiological features and marked biochemical improvement, a core biopsy was pursued to rule out alternative diagnoses. The biopsy confirmed the diagnosis of paraganglioma. Repeat plasma metanephrines measured under alpha and beta blockade outpatient and post biopsy were normal. A multidisciplinary discussion involving Endocrinology, Surgery and Radiology reviewed prior imaging from 2019, which revealed that the lesion had been present, albeit small and distinct from the adrenal gland. Surgical resection of the now-enlarged para-aortic mass was determined to be complex, requiring nephrectomy due to renal vein thrombosis. The consensus was for repeat imaging to assess the renal vein thrombosis for any evolution, which would influence surgical plan. Six months later, the mass gradually reduced in size to 3.2 x 2.7cm. This reduction was attributed to initial tumor hemorrhage, subsequent infarction, and tumor resorption. He is planned for surgical resection and in the interim, remains on alpha and beta blockade. This case illustrates how tumor infarction led to normalized metanephrine levels, with initial hypotension and subsequent hypertension likely due to tumor hemorrhage and a catecholamine surge respectively. It underscores key concepts in paragangliomas, including their diverse presentations, triggers for hypertensive crises, and the relationship between tumor size and metanephrines levels. Presentation: Sunday, July 13, 2025