B先生是一名被诊断为HER2阳性胃食管腺癌转移的56岁男性患者。在重新分期影像显示疾病进展之前，他接受了一线亚叶酸钙、5-氟尿嘧啶和奥沙利铂（FOLFOX）以及曲妥珠单抗治疗了10个月。继续治疗期间，他入院数次，这些入院和他的癌症治疗无关。他在应激激素剂量递减和预防性噻嗪甲唑嗪治疗下在一次肺炎后出院。康复后，他接受了第四次化疗。大约一周后，体格检查发现呼吸困难出现喘鸣声，他接受了为期5天的左氧氟沙星治疗。与此同时，他也完成了应激激素剂量递减。化疗剂量给药后12天，他因呼吸困难逐渐加重和干咳持续3至4天而前往急诊室，而左氧氟沙星治疗结束后症状未见改善。CT扫描显示肺泡浸润增加和多发性实变区域。血液、鼻腔和痰液培养结果均为阴性。支气管镜检查未发现提示毛细血管炎的发现。最终，他被诊断为药物诱发的肺炎/间质性肺疾病（ILD）。尽管持续静脉使用激素，B先生的低氧性呼吸衰竭不断恶化。他被转至住院疗养院，在2周后去世。应考虑对所有接受曲妥珠单抗治疗并出现呼吸困难或其他呼吸相关症状的患者进行药物诱发的肺炎/ILD的鉴别诊断。© 2023 Harborside™。

Mr. B is a 56-year-old man diagnosed with metastatic HER2-positive gastroesophageal adenocarcinoma. He received front-line leucovorin, 5-fluorouracil, and oxaliplatin (FOLFOX) and trastuzumab for 10 months before restaging imaging revealed progressive disease. He then received second-line trastuzumab deruxtecan. His treatment was complicated by several admissions felt to be unrelated to his cancer therapy. He was discharged after an episode of pneumonia on a steroid taper with prophylactic trimethoprim/sulfamethoxazole. Once he recovered, he was given a fourth dose of chemotherapy. About a week later, wheezes were noticed on physical exam, and he was given a 5-day course of levofloxacin. Around the same time, he also finished his steroid taper. Twelve days after his dose of chemotherapy, he presented to the emergency room with 3 to 4 days of progressive shortness of breath and dry cough following the completion of levofloxacin without symptom improvement. A CT scan showed increasing airspace opacities and multifocal areas of consolidation. Blood, nasal, and sputum cultures were negative. A bronchoscopy was performed that did not reveal findings concerning for capillaritis. He was ultimately diagnosed with drug-induced pneumonitis/interstitial lung disease (ILD). Mr. B continued to experience worsening hypoxic respiratory failure despite continuous IV steroids. He was discharged to an inpatient hospice facility where he passed away 2 weeks later. Drug-induced pneumonitis/ILD should be considered in all patients receiving trastuzumab deruxtecan who develop progressive shortness of breath or other respiratory complaints.© 2023 Harborside™.