Obstructive sleep apnea and tricyclic antidepressant use presenting as a pseudopheochromocytoma in an active duty sailor: a case report.

A 36-year-old active duty male with migraine headaches presented for evaluation of poorly controlled hypertension. The workup included an endocrinological examination, which revealed a moderately elevated urine normetanephrine level, suggesting the possibility of a pheochromocytoma. The evaluation also included a sleep study for possible obstructive sleep apnea (OSA) because of a history of snoring, apneic episodes, and daytime somnolence. The sleep study confirmed the diagnosis of OSA. The patient was treated with continuous positive airway pressure therapy and a plasma normetanephrine level demonstrated improvement, but persistent elevation. The patient was noted to be taking amitriptyline for migraine headache prevention. With approval from Neurology, the medication was discontinued and a repeat urine normetanephrine level revealed normalization. This case demonstrates the well-documented medication-associated false-positive test result that can be seen in patients taking tricyclic antidepressants. Tricyclic antidepressants, along with phenoxybenzamine, account for 41 to 45% of all elevated metanephrine and normetanephrine levels in patients without pheochromocytoma. This case also shows that patients with OSA can develop hypertension through elevated sympathetic tone, mimicking a pheochromocytoma. Treatment with continuous positive airway pressure therapy is recommended to not only improve hypertension and catecholamine excess but also distinguish the condition from a pheochromocytoma.