Abstract
A 73-year-old man who presented with nonspecific general symptoms and cognitive impairment was initially diagnosed with mild cognitive impairment due to dementia with Lewy bodies (DLB) based on a reduced blood flow in the parietal and occipital lobes on single-photon emission computed tomography (SPECT) imaging. However, the patient later presented with hyponatremia and hypoglycemia, leading to impaired consciousness, and was diagnosed with isolated adrenocorticotropic hormone deficiency (IAD). Hydrocortisone treatment improved the blood test scores and general symptoms, including cognitive impairment. IAD may show a DLB-like presentation on cerebral blood flow SPECT; therefore, caution is required for the correct diagnosis of IAD.