Fatal Familial Insomnia Initially Developing Parkinsonism Mimicking Dementia with Lewy Bodies.

We report a rare case of fatal familial insomnia in a 58-year-old man who initially developed parkinsonism, secondary dementia, and visual hallucinations that were suspected to be due to dementia with Lewy bodies. We evaluated the function of the striatum via dopamine transporter single-photon emission computed tomography (DAT SPECT) using 123I-ioflupane and found marked presynaptic dopamine dysfunction in the bilateral striatum. This is the first reported case in which the initial symptom of fatal familial insomnia was parkinsonism and in which the dopamine transporter function was evaluated by DAT SPECT.