B80-6-18 Dasatinib-Induced Organizing Pneumonia Presenting as Persistent Pneumonia in Chronic Myeloid Leukemia (CML)

Abstract Introduction Organizing pneumonia (OP) is a rare but recognized pulmonary toxicity associated with tyrosine kinase inhibitors (TKIs), including dasatinib. Differentiating drug-induced OP from infectious or malignant etiologies is essential, as prompt recognition and withdrawal of the offending agent can lead to significant improvement. Case Description A 71-year-old man with chronic myeloid leukemia (CML) on dasatinib therapy (initiated November 2023), presented with six months of persistent productive cough, chest tightness, and recurrent pneumonia unresponsive to multiple antibiotic courses and a prior prednisone taper. He denied recent hospitalizations or intravenous antibiotics. His smoking history included half a pack daily with a 45 pack-year cumulative exposure, and he reported occupational pesticide exposure from working in a greenhouse for 45 years.Chest CT in November 2023 demonstrated clusters of tiny cysts surrounding the vessels and bronchi in the lingular segment, unchanged from prior imaging. CTA of the chest in September 2025 revealed extensive multilobar pneumonia, most pronounced in the left lower lobe, without evidence of pulmonary embolism. Despite empiric ceftriaxone, doxycycline, and systemic corticosteroids (40 mg daily), his symptoms persisted, and oxygen requirements increased.Bronchoscopy with transbronchial biopsy showed fibroinflammatory changes with organizing fibrosis and increased collagen deposition. Special stains were negative for infectious organisms. Immunohistochemistry demonstrated benign alveolar and bronchial epithelium with a predominance of CD5-positive T cells, consistent with a T-cell–mediated inflammatory process. Pathology confirmed organizing pneumonia without evidence of malignancy or granulomatous inflammation.Given the absence of infectious or neoplastic causes, dasatinib-induced organizing pneumonia was suspected. The patient was discharged on home supplemental oxygen and continued corticosteroids with a prolonged taper. Oncology discontinued dasatinib and arranged outpatient follow-up for ongoing management. Discussion Dasatinib, a second-generation BCR-ABL tyrosine kinase inhibitor, is associated with several pulmonary toxicities, including pleural effusion, pulmonary hypertension, and, less commonly, organizing pneumonia. The mechanism likely involves immune-mediated alveolar injury leading to fibroblast proliferation and intra-alveolar organization. Diagnosis requires clinical, radiologic, and histopathologic correlation after exclusion of infection and malignancy. Withdrawal of the offending agent and corticosteroid therapy typically result in clinical and radiologic improvement. Conclusion This case highlights dasatinib-induced organizing pneumonia as a reversible cause of persistent pneumonia in patients receiving TKIs. Clinicians should maintain a high index of suspicion for drug-induced lung injury in patients with non-resolving pulmonary infiltrates to enable timely diagnosis and management. This abstract is funded by: None