MON-004 A Family Affair: A Case of Fraternal Twins Diagnosed With SDHB-Related Hereditary Paraganglioma Syndrome

Abstract Disclosure: P. Saad: None. P. Itersky: None. M. Dominic: None. M. Camelo Pereira: None. S. Sternlieb: None. Paragangliomas are rare neuroendocrine tumors that develop outside of the adrenal glands and can be either functional or nonfunctional in terms of secreting catecholamines. The majority of paragangliomas are sporadic, with approximately one-third to one-half being associated with inherited syndromes such as VHL disease, MEN2, or NF1. A subtype of paraganglioma, known as familial paraganglioma, is caused by pathogenic variants, most notably PGL1, PGL3, and PGL4, which account for majority of familial cases. The most common of these are PGL1, caused by a mutation in the succinate dehydrogenase subunit D (SDHD) gene, and PGL4, caused by a mutation in the SDH subunit B (SDHB) gene. We present the case of three family members, including a set of fraternal twins and their biological father, who were all tested for the SDHB mutation after one family member complained of back pain. A 20-year-old male, who presented with a chief complaint of back pain and no other symptoms, underwent a CT scan that revealed a tumor. This was diagnosed as a retroperitoneal paraganglioma after genetic testing identified a pathogenic SDHB mutation. The patient’s family members, including his fraternal twin brother, biological father, and mother, underwent genetic testing, and all males in the family were found to be positive for this mutation. The patient’s fraternal twin brother was also found to have a retroperitoneal tumor and underwent a robotic lymphadenectomy of the retroperitoneum, with pathology results confirming paraganglioma. Care was coordinated with Oncology, and guideline recommendations were implemented. The lack of reported literature involving a familial case of SDHB mutation in fraternal twins highlights the importance of sequential diagnosis and adherence to guidelines related to testing, treatment, and follow-up. This case underscores the need for endocrinologists to recognize and manage rare neuroendocrine tumors, including familial paragangliomas. Presentation: Monday, July 14, 2025