Pheochromocytoma presenting with hyperosmolar hyperglycemic state and transient stroke-like deficits

Catecholamine excess can disrupt glucose metabolism, but presentation with hyperosmolar hyperglycemic state and transient focal neurologic deficits is uncommon. A 37-year-old man with obesity, hypertension, and prediabetes presented with slurred speech and right arm weakness. Serum glucose was 1252 mg/dL (International System of Units (SI): 69.5 mmol/L) (reference range, 70-99 mg/dL [SI: 3.9-5.5 mmol/L]), serum osmolality was 325 mOsm/kg (reference range, 275-295 mOsm/kg), and hemoglobin A1c was 16.1% (SI: 152 mmol/mol) (reference range, 4.0-5.6% [SI: 20-38 mmol/mol]). Computed tomography angiography and perfusion imaging showed no cerebral ischemia, and the deficits resolved with correction of hyperosmolarity. Because of severe hypertension and abrupt deterioration in glycemic control, plasma metanephrines were measured and found to be markedly elevated, prompting imaging that identified an 8.4-cm right adrenal mass. After α-adrenergic blockade and glycemic optimization, robotic adrenalectomy was performed. Pathology confirmed a 9-cm pheochromocytoma with classic zellballen architecture and a Ki-67 index of approximately 1%. Within 3 weeks, hypertension and insulin-requiring diabetes resolved, allowing discontinuation of all antihypertensive and glucose-lowering medications. This case highlights pheochromocytoma as a reversible cause of severe dysglycemia and a probable metabolic stroke mimic.