Pheochromocytoma as the Index Presentation of Multiple Endocrine Neoplasia Type 2B in a Young Woman with New-Onset Diabetes Mellitus: A Case Report

Background Pheochromocytoma is a rare catecholamine-secreting neuroendocrine tumour of the adrenal medulla that can present with episodic headaches, palpitations, sweating, and hypertension. Catecholamine excess can induce hyperglycemia by suppressing insulin secretion and promoting hepatic gluconeogenesis, thereby mimicking primary diabetes mellitus. Approximately 40% of pheochromocytomas harbour a hereditary basis, most notably in the context of Multiple Endocrine Neoplasia type 2 (MEN2) syndromes caused by activating mutations of the RET proto-oncogene. Case Presentation: A 35-year-old female presented with a four-month history of episodic headaches, palpitations, sweating, and dizziness, alongside recently diagnosed diabetes mellitus. Clinical examination revealed resting tachycardia and significant orthostatic hypotension. Biochemical evaluation demonstrated markedly elevated urinary and plasma metanephrines, and cross-sectional and functional imaging confirmed a unilateral adrenal mass. A family history of medullary thyroid carcinoma prompted genetic testing, which revealed a RET proto-oncogene mutation consistent with MEN2B syndrome, despite the absence of classical phenotypic features such as mucosal neuromas or marfanoid habitus. The patient underwent successful laparoscopic adrenalectomy following adequate adrenergic blockade. Conclusion This case highlights the importance of suspecting pheochromocytoma as a secondary cause of new-onset diabetes in young patients presenting with episodic sympathoadrenal symptoms. Systematic genetic evaluation of all pheochromocytoma patients is essential to identify hereditary syndromes, enabling timely surveillance and screening of at-risk family members.