OBJECTIVES Atypical variants are rare in genetically determined Alzheimer disease (AD). This case describes a patient with Down syndrome-associated Alzheimer disease (DSAD) who presented with symptoms of posterior cortical atrophy (PCA). METHODS We conducted a clinical and cognitive evaluation, APOE genotyping, determination of AD biomarkers in CSF, structural MRI, [18F]FDG-PET, and tau-PET ([18F]PI2620) scans. RESULTS A 39-year-old man with DS and mild intellectual disability presented with progressive visuoperceptual disturbances over 18 months. Examination revealed global cognitive impairment, with notable visual agnosia and neglect. The patient also exhibited significant constructive and oculomotor apraxia, optic ataxia, alexia, agraphia, and prosopagnosia. The patient was determined to be APOE3 homozygous, and CSF analysis was consistent with AD pathophysiology. T1-weighted MRI revealed predominant parieto-occipital atrophy. FDG-PET showed significant bilateral hypometabolism in the parietotemporal and occipital cortices, and tau-PET demonstrated pathologic uptake in the parietal, precuneus/posterior cingulate, lateral temporal, and occipital cortices. DISCUSSION This well-characterized case of PCA syndrome due to AD in a very young patient with DS demonstrates the occurrence of atypical presentations in DS that might be overshadowed by the baseline intellectual disability associated with DS.

中文翻译：

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唐氏综合症患者阿尔茨海默病引起的后皮质萎缩：病例报告。


目的 非典型变异在遗传性阿尔茨海默病 （AD） 中罕见。该病例描述了一名唐氏综合征相关阿尔茨海默病 （DSAD） 患者，该患者表现为后皮质萎缩 （PCA） 症状。方法 我们进行了临床和认知评估、APOE 基因分型、CSF 中 AD 生物标志物的测定、结构 MRI、[18F]FDG-PET 和 tau-PET （[18F]PI2620） 扫描。结果 一名 39 岁的 DS 男性轻度智力障碍在 18 个月内出现进行性视觉感知障碍。检查显示整体认知障碍，伴有明显的视觉失认和忽视。患者还表现出明显的建设性和动眼神经失用症、视神经共济失调、失语症、失写症和面容失认症。患者为 APOE3 纯合子，CSF 分析与 AD 病理生理学一致。T1 加权 MRI 显示主要的顶枕萎缩。FDG-PET 显示顶颞叶和枕叶皮层显着的双侧代谢减退，tau-PET 显示顶叶、楔前/后扣带回、外侧颞叶和枕叶皮层的病理摄取。讨论 这例特征明确的 AD 引起的 PCA 综合征病例发生在一名非常年轻的 DS 患者中，表明 DS 中出现了非典型表现，这些表现可能被与 DS 相关的基线智力障碍所掩盖。