[A case of Down's syndrome with progressive dementia of Alzheimer type].

A rare case of Down's syndrome complicated with progressive dementia of Alzheimer type in a 41-year-old man was reported. On 123I-IMP SPECT, the patient revealed symmetrical bilateral temporo-parietal hypoperfusion. This finding seemed to support the developing dementia of Alzheimer type on the basis of clinical manifestations. 123I-IMP SPECT seemed to be useful for early diagnosis of Alzheimer-like change in a natural course of Down's syndrome.