Abstract:

In 2022, the total number of patients with Alzheimer's disease (AD) and related dementias in China was approximately 16 million, and it is projected to exceed 20 million by 2030, ranking fifth among the diseases that cause death. Early and accurate diagnosis is essential for its treatment and overall management. The majority of AD patients exhibit the typical features of hippocampal amnestic syndrome, while some patients may present with atypical features characterized by early manifestations such as visuospatial impairment, language impairment, executive dysfunction or beha-vioral abnormalities, and sensorimotor deficits, posing challenges for clinical diagnosis. In a neuropathologically confirmed early-onset AD cohort, the misdiagnosis rate for patients with atypical manifestations reaches 53%, whereas that for patients with typical symptoms is only 4%. This article systematically elaborates on the clinical features, key diagnostic points, and differential diagnosis of four atypical AD subtypes: posterior cortical atrophy variant, primary progressive aphasia variant, frontal variant, and corticobasal syndrome variant. Through medical history collection, physical examination, and systematic review, combined with neuropsychological assessment and neuroimaging, clinicians can identify cognitive-behavioral syndromes and clinical-imaging syndromes, thereby recognizing and differentiating patients with typical and atypical manifestations of AD. As the clinical application of biomarkers becomes increasingly widespread, it will promote a deeper understanding of AD clinical manifestations. This will help clinicians in the early recognition of atypical symptoms, thereby providing support for accurate diagnosis, timely intervention, and individualized care for patients with atypical AD.

Key words: Alzheimer's disease, Clinical phenotype, Neuroimaging, Biomarker