Isolated left adrenal medullary hyperplasia.

A 44-year-old Japanese man was referred to our hospital for the evaluation of paroxysmal hypertension. 123I-metaiodobenzylguanidine (MIBG) single-photon emission computed tomography (SPECT) revealed specific uptake in the left adrenal gland in addition to high levels of serum and urinary catecholamines although computed tomography and magnetic resonance imaging were not able to detect a definite adrenal mass. Left adrenalectomy was performed and he was diagnosed with adrenal medullary hyperplasia (AMH). A diagnosis of unilateral AMH is important because AMH resection can effectively treat hypertension. <Learning objective: Isolated unilateral adrenal medullary hyperplasia (AMH) is a relatively rare disease that causes hypertension, and is generally diagnosed only after catecholaminergic symptoms mimicking pheochromocytoma. However, a diagnosis of unilateral AMH is important because AMH resection can effectively treat hypertension. 123I-MIBG-SPECT is an important diagnostic modality for a diagnosis of unilateral AMH even though computed tomography and magnetic resonance imaging are not able to detect a definite adrenal mass.>.