Abstract Introduction Chemotherapy-induced pneumonitis is a rare but serious complication of cancer treatment. It typically presents with bilateral lung infiltrates. Unilateral involvement is uncommon and may lead to misdiagnosis, delaying appropriate therapy. Case Presentation A 68-year-old woman with HER2-positive left breast cancer on trastuzumab, pertuzumab, and paclitaxel (THP) (last dose 2 weeks prior)— presented with one week of progressive dyspnea, dry cough, and light-headedness. Her past medical history included hypertension and remote stage I non-small cell lung cancer treated with right lobectomy in 2012. On arrival, she was hypoxic (SpO2 67% on room air), requiring high-flow oxygen. Physical examination revealed diffuse rhonchi and use of accessory muscles. Labs showed leukocytosis (12 × 109/L), hyponatremia (Na 126 mmol/L), and BNP 800. CTA chest revealed bilateral segmental pulmonary emboli and extensive right-sided ground-glass opacities with superimposed alveolar opacities, along with smaller peripheral opacities also seen in the left upper lobe. TTE showed normal LVEF, moderate right ventricular dilation with strain, and a small-to-moderate pericardial effusion. She was initially managed for presumed multifactorial acute hypoxic respiratory failure secondary to PE, pneumonia, and possible heart failure. Treatment included anticoagulation, antibiotics, and diuretics. However, repeat high-resolution CT after diuresis showed persistent, predominantly right-sided opacities. BAL from bronchoscopy demonstrated right-sided airway inflammation without evidence of infection. Given her recent THP chemotherapy and lack of improvement with antibiotics or diuresis, drug-induced pneumonitis was suspected. High-dose corticosteroids were initiated, leading to marked improvement in oxygenation. She was discharged in stable condition on anticoagulation, a steroid taper, and 3L nasal cannula with close outpatient follow-up. Discussion Unilateral presentations of chemotherapy-induced pneumonitis are extremely rare and can delay diagnosis. In this case, right-lung predominant infiltrates led to initial treatment for infection and PE. The lack of response to standard therapies and negative infectious workup were key to considering drug-induced lung injury, avoiding unnecessary prolonged antibiotic exposure and guiding timely corticosteroid therapy. This abstract is funded by: none
Yassin et al. (Fri,) studied this question.