Undiagnosed Pheochromocytoma Simulating Malignant Hyperthermia

INTRODUCTIONPheochromocytomas are rare catecholamine-producing neuroendocrine tumors. They are surgically curable but can be lethal if remain undiagnosed. We report a patient earlier diagnosed with malignant hyperthermia but later found to have pheochromocytoma on autopsy. CASE REPORTAfter a preprocedural pain block for elective right shoulder arthroscopy, a 53-year-old hypertensive white man developed chest pain. In the operating room, he had increased blood pressure. Postoperatively, his blood pressures dropped from 220/100 to 80/30 mm Hg. He later developed high fever with core temperature reaching a peak of 42.2°C, rapid breathing, and died after unsuccessful attempts to stabilize him. AUTOPSYAutopsy revealed a tumor in his right adrenal gland, measuring 10 cm in greatest dimension and weighing 530 g. It was red brown with a hemorrhagic and cystic cut surface. A thin rim of yellow-orange adrenal cortex was visible at the margin of the tumor, indicating that it originated from the underlying adrenal medulla. The left adrenal gland was unremarkable.Sections showed hypercellular tumor with zellballen architecture. The tumor cells were round to oval with finely granular basophilic cytoplasm and mild pleomorphism. A 24-hour urine sample collected before his death showed greater than 22727 μg/g Ratio to Creatinine metanephrines and normetanephrine, indicating that the tumor was active and secreted high levels of catecholamine. The cause of death was established as the complications of pheochromocytoma in the settings of general anesthesia for shoulder arthroscopy. The manner of death was natural. CONCLUSIONSPheochromocytoma can mimic malignant hyperthermia, and it should always be considered and managed appropriately in such scenarios to avoid untoward consequences. Pathologists must also be aware of this when conducting an autopsy in cases with a previous clinical diagnosis of malignant hyperthermia.