Rationale: Chronic eosinophilic pneumonia (CEP) is rare and an idiopathic disorder. The disease has been associated with drugs, infection, or irradiation, and its relationship with asthma remains unclear.
Patient concerns: We reported a case of a 49-year-old female patient after trastuzumab and radiation therapy for breast cancer. Two months after radiation treatment, the patient complained of productive cough, progressive breathlessness, occasional wheezing, and left pectoralgia.
Diagnoses: Computed tomography (CT) scan revealed infiltrates in lungs. Without evidence of infection, marked increased eosinophils in a transbronchial biopsy performed from the left upper lobe confirmed the diagnosis of CEP after trastuzumab and radiation therapy.
Interventions: The patient was started with oral prednisone at 0.5 mg/kg/day.
Outcomes: A CT scan of the chest obtained 2 weeks after steroid treatment showed diminishment of the lesions, and at the 6-month follow-up, the patient had no complaints of discomfort with no relapse of pulmonary lesions.
Lessons: Physicians should consider CEP as a diagnosis in patients who have had previous exposure to trastuzumab and radiation therapy, especially with a history of asthma. Timely diagnosis and treatment may benefit these patients.