ABSTRACT
Introduction: Acute eosinophilic pneumonia (AEP) is an uncommon lung disease. Its incidence and epidemiology remain understudied till date. The hypothesized etiology of AEP is an acute hypersensitivity reaction to an inhaled antigen such as tobacco smoke and other peculiar environmental factors. Vaccines as triggers of AEP, albeit very rare, have been reported in the literature. Case presentation: A 64-year-old male with history of hyperlipidemia on atorvastatin presented to the emergency room with complaints of cough productive of pink tinged sputum, exertional shortness of breath, chills and fever with maximum recorded temperature of 101 °F. His symptoms started within a few hours of receiving tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine two days ago. He denied any recent travel. He was a lifelong non-smoker and was employed as hospital case manager. His vitals were significant for tachycardia 116/min, tachypnea 30 breaths/min and SaO2 of 93 % on 10L. On physical examination, he was noted to have coarse and diminished breath sounds in both lung fields. Initial lab work showed elevated leukocyte count of 20.4 k/uL with absolute eosinophil count of 1.6 k/uL. Other labs were unremarkable. Diffuse bilateral reticulonodular and alveolar opacities were visualized on chest X-ray. Computed tomography (CT) of the chest showed profuse pulmonary nodules, scattered ground glass opacities and septal thickening concerning for bilateral multifocal pneumonia (figure 1). Blood cultures and sputum cultures were obtained and he was empirically treated with ceftriaxone and azithromycin. Sputum eosinophil smear was positive raising concerns for fungal and parasitic infections. Cultures remained negative and his hypoxia worsened. Thus, infectious diseases and pulmonology were consulted. Extensive infective disease work-up for bacterial, fungal, parasitic and viral pathogens came back negative. CT guided biopsy of a lung nodule demonstrated interalveolar eosinophil and fibrin deposition consistent with eosinophilic pneumonia (figure 2). Patient was started on glucocorticoids with dramatic improvement in his symptoms, imaging and oxygen needs. With his symptom onset following Tdap vaccine and negative infective work-up, AEP was suspected to be triggered by the vaccine. Discussion: AEP provoked by vaccination is rare. Cases have been reported with influenza, pneumococcal and also COVID-19 vaccines. To the best of our knowledge, this is the first report of AEP following Tdap vaccine in adults. Only up to 30% of patients with AEP will have peripheral eosinophilia. Diagnosis is usually confirmed on lung biopsy and patients respond very well to glucocorticoids.