Logopenic variant of primary progressive aphasia in a bilingual non-Alzheimer's disease octogenarian.

A highly educated and intellectually active 84-year-old male presented with word-finding pauses and impaired sentence repetition, with preserved single-word comprehension, reading, and writing, a clinical profile consistent with the logopenic variant of primary progressive aphasia (lvPPA). Interestingly, the initial symptom was difficulty with auditory verbal comprehension in Portuguese, his second language, while comprehension in English remained initially preserved. Structural and functional imaging revealed no atrophy in the temporoparietal region or cortical hypometabolism. Plasma biomarkers, including Aβ42/40 and plasma-measured tau phosphorylated at threonine 217 (p-tau217), were within normal limits, arguing against biological Alzheimer's disease (AD). This case illustrates a rare constellation of findings - bilingual asymmetry, negative AD biomarkers, and unremarkable neuroimaging - suggestive of a non-Alzheimer's pathology. Alternative etiologies such as primary age-related tauopathy (PART) and argyrophilic grain disease (AGD) are discussed, emphasizing the utility of fluid biomarkers in distinguishing phenocopies within the lvPPA spectrum.