SUN-494 Large Pheochromocytoma and Successful Twin Pregnancy: Case Report

Abstract Disclosure: A. Alexandre Pereira: None. M. Wohlfahrt Baumgarten: None. M. Czepielewski: None. S. Pinho Silveiro: None. Background: Pheochromocytoma/paraganglioma (PHEO/PPGL) is a rare catecholamine-secreting tumor, complicating less than 0.001% of pregnancies, with even fewer cases reported in twin pregnancies. This condition presents diagnostic challenges due to overlapping symptoms with common pregnancy-related disorders, like preeclampsia. Most cases described are of patients with PHEO/PGL diagnosed before pregnancy. We report a rare case of PHEO/PGL diagnosed at the 27th week of a twin pregnancy with favorable outcome of live births, in a tertiary university hospital in southern Brazil. This case presentation follows the CARE guidelines. Case Report: A 38-year-old woman at 27 weeks of dichorionic-diamniotic twin pregnancy presented at the emergency unit with persistent hypertension, tachycardia, and paroxysmal headaches, that lasted up to 30 minutes and occurred multiple times per week, becoming frequent since the 20th week of pregnancy. Initial tests revealed no evidence of target organ damage, and proteinuria was absent. Initial treatment with metoprolol worsened the hypertensive crises, prompting further evaluation. Biochemical assays revealed high 24-hour urinary metanephrines (10,977.7 µg; nl <280 µg) and normetanephrines (833.8 µg; nl <732 µg). MRI confirmed a cystic adrenal lesion (8.4 x 8.3 x 7.5 cm) displacing adjacent organs, consistent with PHEO/PGL. Management included doxazosin (titrated to 6 mg/day) for alpha-blockade, followed by metoprolol succinate to control heart rate. Hypertension control and maternal-fetal monitoring ensured fetal growth and stability without additional maternal risk. In this scenario it was decided to perform adrenal surgery after pregnancy. At 37 weeks, a cesarean delivery was performed, resulting in healthy twins: one weighed 2,410 g (APGAR 8/10) and the other 2,155 g (APGAR 9/10). The anesthetic procedure during the cesarean section had no complications, even with the twin birth, maintaining stable maternal blood pressure and heart rate. Lactation was stimulated postpartum, but breastfeeding began only after adrenalectomy and stopping alpha and beta blockers. A total left adrenalectomy was performed 10 days postpartum. Histopathological examination and immunohistochemistry confirmed the diagnosis of PHEO/PGL. Postoperative recovery was successful, with normal biochemical markers and symptom resolution. Conclusion: This case highlights the importance of early distinction between PHEO/PGL and hypertensive disorders of pregnancy. MRI without gadolinium and biochemical testing are pivotal for diagnosis. Alpha-blockade followed by beta-blockade remains the cornerstone of preoperative management, with doxazosin preferred for its safety profile in pregnancy. Surgery timing should consider gestational age, tumor size, and maternal stability. Multidisciplinary care is essential to optimize maternal and fetal outcomes. Presentation: Sunday, July 13, 2025