Diagnosis of pheochromocytoma in the setting of Parkinson disease

Background. A 59-year-old man with a 7-year history of Parkinson disease (PD) presented with episodes of sudden, severe headaches with neck pain, tachycardia, sweating and pallor. During these episodes, the patient showed marked elevations in blood pressure, regardless of posture. This was unusual, given that he had no prior history of hypertension. The array of symptoms raised suspicions of pheochromocytoma, but diagnosis was challenging, as the standard diagnostic biochemical tests were confounded by dopaminergic medications. Further work-up revealed left adrenal medullary hyperplasia. Several reports exist of pseudopheochromocytoma in patients on dopaminergic therapy, but this is the first documented case of pheochromocytoma syndrome due to adrenal medullary hyperplasia in a patient with PD. This case highlights the challenges of performing a diagnostic work-up in a PD patient with symptoms suggestive of pheochromocytoma, and illustrates the utility of ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) single-photon emission CT in making a diagnosis. Investigations. Physical examination, laboratory tests, abdominal MRI scan, abdominal ¹²³I-MIBG scan, abdominal ¹⁸F-fluorodeoxyglucose PET scan. Diagnosis. Pheochromocytoma syndrome due to adrenal medullary hyperplasia. Management. Surgical excision of the left adrenal gland.