A 40-Year-Old Woman With Exertional Dyspnea and Unexplained Hypoxia.

A 40-year-old woman presented with a 3-week history of progressive exertional dyspnea. She had previously been active, but her symptoms progressed to the point where she was short of breath with walking. Her oxygen level was 90% at rest and decreased to 70% to 80% after exertion. The patient denied fever, cough, sputum production, edema, syncope, or other clinically remarkable symptoms. No significant weight loss was noted recently. Two and a half years ago, the patient was diagnosed with stage IV poorly differentiated lung adenocarcinoma (cT2N3M1c) with a 70% PD-L1 expression level, along with metastases to the pelvis, liver, brain, and bone. The patient received sequential ROS1-targeted therapy (crizotinib, entrectinib, repotrectinib) plus local therapies for metastatic lesions. A tumor assessment 2 months prior showed stable disease. She had no history of smoking, substance misuse, or alcohol consumption. No family history of genetic diseases was reported.