Unmasking Hypersensitivity Pneumonitis: A Complex Case of Environmental Exposures and COVID-19

Abstract Introduction:Hypersensitivity pneumonitis (HP) is an immunologically mediated lung disease caused by repeated inhalation of organic antigens or certain chemical agents. The condition triggers an immune response, leading to inflammation of the lung parenchyma and bronchioles. Herein we describe a case of a 41-year-old male with known exposure to a racing pigeon, as well as to a toxic waste management facility suspected to have developed HP shortly after exposure to his racing pigeon and being infected by COVID-19. Case:A 41-year-old male with a medical history of asthma, ulcerative colitis (managed with Adalimumab), initially presentation to the emergency department (ED) a month prior with symptoms of cough, cold, and bronchospasms unresolved by home asthma inhalers. He tested positive for COVID-19 at that time and was treated with benzonatate and Combivent. Patient presented again to ED with worsening dyspnea, cough, wheezing, congestion, and night sweats, accompanied by severe nocturnal cough-induced headaches and variable sputum production and a syncopal episode following a severe coughing fit. Subsequent investigation discovered that the patient had a racing pigeon, and his symptoms seem to coincide with when he first started taking care of the bird. Patient also has known exposure to a toxic waste management facility. Hypersensitivity pneumonitis panel was positive for pigeon serum ABS. IgE was elevated at 635 IU/mL. Eosinophil percentage was highest at 5.8% corresponding to a count of 0.54 K/uL. CT lungs without contrast showed bilateral mosaic attenuation, most pronounced in the upper lobes. The patient was treated with prednisone burst therapy and given strict instructions for trigger avoidance. He was doing very well on clinic follow-up 1.5 weeks after finishing his prednisone taper. He continued to take fluticasone/salmeterol, which he believes helps. He still had environmental exposure to his racing pigeon, however, had been limiting exposure as compared to before. He still had exposure to dust, nearby asphalt, and waste processing facility, which he believes is the most powerful trigger for his symptoms. Discussion:The laboratory and imaging findings were consistent with Bird Fancier's Lung. However, other differentials include interstitial lung disease secondary to adalimumab, COVID-19 pneumonitis, or possible asthma exacerbation. This case underscores the importance of surveying for environmental exposures in dyspneic patients especially when symptoms are persistent despite treatment. This also highlights that respiratory viral infections, and in this scenario, COVID-19, may contribute to the development of hypersensitivity pneumonitis.