Progressive supranuclear palsy (PSP) is a neurodegenerative disorder with diverse clinical phenotypes characterized by supranuclear gaze palsy, parkinsonism with postural instability, and frontal dementia. The early and accurate diagnosis of PSP remains difficult because of the variable combination of symptoms and frequent lack of gaze abnormalities early in the disease course. Moreover, a subset of PSP shows behavioral changes as the initial presentation, which considerably overlaps with the clinical picture of frontotemporal dementia (FTD). Thus, this subgroup possibly needs psychiatric assessments. Here, we describe a clinical case of PSP difficult to differentiate from FTD because the frontal presentation persisted without gaze palsy until the late stage of the clinical course. A 58-year-old man was admitted to our hospital for the reconsideration of a diagnosis of FTD. Disinhibited and gambling behaviors inconsistent with his previous personality first appeared at around the age of 45, with gradual progression, followed by memory deficits, executive dysfunction, and a slowing of mental processes. Recurrent sexual disinhibition led him to undergo psychiatric consultation at the age of 57. Downward gaze palsy and postural instability with recurrent falls emerged 8 months after the first psychiatric examination, and he was clinically diagnosed with PSP 13 years after the initial frontal presentation. PSP should be considered in the differential diagnosis of patients presenting with frontal lobe symptoms, even in psychiatric practice.
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