Abstract
Introduction Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by chronic exposure to a variety of occupational and environmental antigens. Diagnosis is made through history of antigen exposure and characteristic imaging findings, though some cases require alveolar fluid analysis or lung biopsy. We present the case of a man who developed HP after exposure to a rarely-documented antigen in the form of pyrethroids present in cockroach spray. Case Description A 47-year-old male presented with a one-year history of dyspnea and cough. CT chest showed mosaic attenuation with areas of groundglass and air-trapping. Infectious and rheumatologic testing was negative, and he denied any known antigen exposure. Due to persistent symptoms without a formal diagnosis, surgical lung biopsy was pursued. Pathology showed lymphocytic airway inflammation and poorly-formed, non-necrotizing granulomas consistent with HP. His symptoms gradually improved with corticosteroids. Additional history-taking revealed he used cockroach spray daily for months without a mask or methods for ventilation. He was counselled on avoidance of further exposure which led to resolution of imaging abnormalities and symptoms. Discussion HP typically presents as an insidious onset of dyspnea, cough, and constitutional symptoms. Imaging often shows patchy areas of parenchymal inflammation and air-trapping adjacent to normal lung tissue in a pattern referred to as the triple density or head cheese sign. Determining a causative antigen is important in making the diagnosis, which emphasizes the need for a thorough history of exposures. Bronchoalveolar lavage and lung biopsy are typically reserved for when symptoms, imaging, and exposure history are inconclusive. Although lung biopsy helped make the diagnosis in our case, a careful history to elicit the patient’s exposure to cockroach spray may have obviated the need for invasive testing. Standardized patient questionnaires are available from guideline societies to assist in documenting exposure history. A better understanding of potential causative antigens of HP may help direct appropriate history-taking. Pyrethroids are a synthetic chemical commonly used in insecticides for crop protection, mosquito netting, and household sprays. There are animal studies demonstrating evidence of organ injury when these chemicals are ingested, but only sporadic case reports showing respiratory injury in humans. The case reports available linking exposure to development of HP primarily occur in pet groomers. Our patient had a clear relationship between exposure and lung injury followed by avoidance and resolution of symptoms. Our case highlights the need for further study of potential HP triggers, especially in the context of commonly used household chemicals. This abstract is funded by: None