目的：首次报道1例在临床实践应用多奈单抗（donanemab），通过正电子发射断层显像（positron emission tomography，PET）定量评估达到停药标准并实现停药的阿尔茨海默病（Alzheimer’s disease，AD）病例。

方法：对1例78岁女性AD患者进行系统评估，监测多奈单抗治疗前后的认知功能、β-淀粉样蛋白（amyloid β-protein，Aβ）及Tau PET影像及MRI变化，并随访不良反应。

结果：患者经6次多奈单抗治疗后，大脑Aβ负荷减低降至7.02 CL，达到停药标准，Tau蛋白沉积较基线视觉轻度减轻。治疗期间蒙特利尔认知评估（Montreal Cognitive Assessment，MoCA）评分由17分提高至21分（主要集中于定向力项目），而其日常生活能力保持稳定。治疗过程中出现无症状性淀粉样蛋白相关影像学异常（amyloid-related imaging abnormalities，ARIA），经随访未进展。

结论：多奈单抗在真实世界条件下可实现深度Aβ清除并维持良好安全性。基于PET定量的个体化疗程具有可行性，但仍需长期随访以评估清除持久性及其对Tau蛋白动态变化和临床结局的影响，为抗Aβ疗法的精准化应用提供参考。

Objective: To report the first real-world case of an Alzheimer's disease patient who achieved PET-defined amyloid clearance sufficient to meet the discontinuation criteria and successfully discontinue donanemab therapy, and to illustrate the feasibility of PET-guided individualized treatment duration in clinical practice.

Methods: A 78-year-old female patient with AD was systematically evaluated before and after donanemab therapy. Cognitive function, amyloid-β (Aβ) and Tau PET imaging, and MRI findings were longitudinally monitored, along with the assessment of treatment-related adverse events.

Results: After six infusions of donanemab, the patient's Aβ load decreased to 7.02 Centiloids (CL), meeting the predefined discontinuation criterion. Tau deposition showed a mild visual reduction compared with baseline. The MoCA score increased from 17 to 21, mainly in the orientation domain, while activities of daily living remained stable. Asymptomatic amyloid-related imaging abnormalities (ARIA) was detected and remained stable during follow-up

Conclusion: This case demonstrates that donanemab can achieve substantial Aβ clearance with favorable safety in real-world settings. PET-based quantitative guidance for individualized therapy duration appears feasible, though long-term follow-up is required to assess the durability of Aβ clearance and its downstream impact on Tau dynamics and clinical outcomes, providing insights for precision application of anti-Aβ therapies.