Severe Pseudomonas aeruginosa Pneumonia in a Breast Cancer Patient Despite Pegfilgrastim Administration.

Pegfilgrastim dramatically reduces febrile neutropenia (FN) caused by high-risk chemotherapy. This report details the presentation of a 72-year-old female who developed a fatal infection of Pseudomonas aeruginosa pneumonia that occurred during preoperative chemotherapy despite pegfilgrastim administration. She was brought to the hospital with symptoms of high fever and general fatigue during chemotherapy, but her respiratory symptoms were minimal, and a chest computed tomography (CT) showed no obvious signs of pneumonia. She had FN. After she was hospitalized, her breathing and consciousness worsened rapidly, and the chest CT showed prominent lobar pneumonia. Her blood cultures suggested P. aeruginosa, so she was quickly switched to meropenem. She was diagnosed with septic shock and acute respiratory distress syndrome due to severe P. aeruginosa pneumonia, and she was started on noninvasive positive pressure ventilation with immunoglobulin preparations. P. aeruginosa developed drug resistance, so it was necessary to change antibiotics. She was discharged without complications of pulmonary fibrosis on chest CT. It is crucial to always be aware that severe infections can occur even with pegfilgrastim administration, promptly identify the causative pathogen, and intervene with early treatment.