A 66-year-old man was admitted with visual impairment, functional disability, and worsening glycemic control. On admission, he had optic atrophy without diabetic retinopathy in both eyes, sensory impairment of the lower extremities, ataxia, and cognitive impairment. As both serum and cerebrospinal fluid tested positive for syphilis, he was diagnosed with neurosyphilis and treated with antibiotics. Functional ability and cognitive function improved after conducting syphilis treatment; we consequently started him on an insulin self-administration program. Two years later, his glycemic control has normalized. Dementia caused by neurosyphilis is one of the most important differential diagnoses of treatable dementia; hence, early diagnosis and early treatment are important.
Keywords: IADL; cognitive impairment; diabetes mellitus; neurosyphilis; treatable dementia.