Mixed primary progressive aphasia and alcohol use disorder: a case of detailed clinical phenotyping outperforming molecular imaging

Primary progressive aphasia (PPA) refers to a group of clinically and pathologically heterogeneous syndromes characterized by progressive and relatively selective impairment in speech and language as the main cognitive domain in the early disease stage. The main clinical variants of PPA based on current diagnostic criteria include logopenic variant PPA (lvPPA), nonfluent variant PPA (nfvPPA), and semantic variant PPA (svPPA). Identification of speech/language and non-language abilities and in vivo biomarkers (such as neuroimaging, genetic, and biofluid studies) facilitates the correct classification of the main variants. PPA variants clinical presentation may overlap leading to a diagnosis of mixed or unclassified PPA. We report the case of a trilingual patient with a 10-year history of word-finding difficulties initially attributed to chronic alcohol abuse. Her clinical presentation was evocative of lvPPA with features of svPPA, while her neuropsychological testing and MRI data were suggestive of a diagnosis of svPPA. While β-amyloid PET brain imaging was negative, postmortem immunohistochemical analysis of the brain showed unequivocal evidence of Alzheimer's disease. We describe this case of complex PPA for which clinical data outperformed imaging biomarkers in predicting the underlying neuropathology and discuss chronic alcohol abuse as a potential risk factor for neurodegeneration.