Pick's disease presenting as progressive apraxia of speech: Atypical clinical and neuroimaging features in three...

Patients with progressive apraxia of speech (PAOS) often develop atypical parkinsonian features suggestive of corticobasal syndrome (CBS) or progressive supranuclear palsy (PSP), and typically have an underlying 4-repeat tauopathy at autopsy. We describe three cases of PAOS with underlying Pick's disease, a 3-repeat tauopathy, who lacked CBS or PSP features during life.

We reviewed patients enrolled in the Neurodegenerative Research Group's ongoing studies on speech and language disorders and identified those with PAOS who had autopsy-confirmed Pick's disease. All patients had comprehensive neurologic, speech-language, and neuropsychological assessments, as well as multimodal neuroimaging, during life.

Three female patients presented with phonetic PAOS without parkinsonism. Patient 1 had speech onset at age 54, later developed behavioral variant frontotemporal dementia (bvFTD), and died at 64. Patient 2 had speech onset at 47, early bvFTD features, prominent frontal and temporal involvement, and died at 53. Patient 3 had speech onset at 58, minimal behavioral changes, primarily frontal involvement on imaging, and died at 63.

Our findings highlight that Pick's disease can present with PAOS and may be distinguished from 4R-tau PAOS by an absence of motoric CBS/PSP features and, in some cases, by prominent temporal hypometabolism with bvFTD development. These atypical features may prove useful in the antemortem identification of Pick's disease as a cause of PAOS.