Two Languages and One Aphasia: A Systematic Scoping Review of Primary Progressive Aphasia in Chinese Bilingual Speakers, and Implications for Diagnosis and Clinical Care

<b>Background/Objectives</b>: Primary progressive aphasia (PPA) is characterised by progressive decline in language and communication. However, existing diagnostic frameworks and assessment tools are largely based on Indo-European languages, which limits their applicability to Chinese bilingual speakers whose linguistic profiles differ markedly in tonal phonology, logographic writing, and bilingual organisation. This review aimed to (a) describe how PPA presents in Chinese bilingual speakers, (b) evaluate how well current speech-language and neuropsychological assessments capture these impairments, and (c) identify linguistically and culturally informed strategies to improve clinical practice. <b>Methods</b>: A systematic review was conducted in accordance with the PRISMA-ScR guidelines. Four databases (PubMed, Scopus, Web of Science, PsycINFO) were searched, complemented by backward and forward citation chaining. Eight empirical studies met the inclusion criteria. Data were extracted on participant characteristics, PPA variant, language background, speech-language and writing profiles, and assessment tools used. Thematic analysis was applied to address the research questions. <b>Results</b>: Across variants, Chinese bilingual speakers demonstrated universal PPA features expressed through language-specific pathways. Mandarin speakers exhibited tone-segment integration errors, tonal substitution, and disruptions in logographic writing. Lexical-semantic degradation reflected homophony and compounding characteristics. Bilingual individuals showed parallel or asymmetric decline influenced by dominance and usage. Standard English-based naming, repetition, and writing assessments did not reliably capture tone accuracy, radical-level writing errors, or bilingual patterns. Sociocultural factors, including stigma, delayed help-seeking, and family-centred care expectations, further shaped diagnostic pathways. <b>Conclusions</b>: Chinese PPA cannot be meaningfully assessed using tools designed for Indo-European languages. Findings highlight the need for tone-sensitive repetition tasks, logographic writing assessments, bilingual diagnostic protocols, and culturally responsive communication-partner support. This review provides a comprehensive synthesis to date on Chinese bilingual PPA and establishes a foundation for linguistically inclusive diagnostic and clinical models.