Abstract Background Hypersensitivity pneumonitis (HP) is an immunologically mediated inflammatory response to the inhalation of organic antigens. Bagassosis, a form of HP first recognized in sugarcane workers, is caused by Laceyella sacchari spores commonly found in bagasse dust, the fibrous residue of sugarcane. Although bagasse exposure is rarely reported outside agricultural settings, bagasse cellulose fibers have resurfaced in insulation materials due to their thermal and acoustic properties. We discuss an unusual case of bagassosis HP in a non-agricultural urban resident. Case Presentation A 35-year-old male, employed as a dog walker, with no significant medical history, presented with two weeks of pleuritic chest pain, dry cough, and exertional dyspnea. The patient reported that two weeks before symptom onset, construction had been performed in his apartment involving drywall removal and exposure of insulation materials. He denied fever, chills, hemoptysis, weight loss, or recent sick contacts. Vital signs were normal and his physical exam was unremarkable. Complete blood count and comprehensive metabolic panel were within normal limits. A CTA chest revealed innumerable solid and subsolid pulmonary nodules up to 1.7 cm without evidence of pulmonary embolism or pleural effusion. A PET scan demonstrated hypermetabolic pulmonary and hepatic lesions, raising concern for metastatic disease. While awaiting autoimmune and HP testing, a CT-guided biopsy of a left lower-lobe lesion showed organizing pneumonia with multinucleated giant cells but no granulomas, fibrosis, or malignancy. Autoimmune testing was negative, but HP serology demonstrated elevated Laceyella sacchari IgG (41.1 µg/mL), confirming bagassosis. He was treated with prednisone 0.5 mg/kg/day with a gradual taper over eight weeks and relocated to a new apartment. Three weeks later, repeat CT showed complete resolution of pulmonary nodules. Discussion Bagassosis, once an occupational hazard of sugarcane processing, may reemerge through modern insulation containing bagasse cellulose fibers. Although marketed as sustainable and non-toxic, bagasse-based materials can provoke hypersensitivity pneumonitis in exposed individuals. The presentation may mimic metastatic disease on imaging, while histopathology typically reveals organizing pneumonia with multinucleated giant cells rather than classic granulomatous inflammation. Diagnosis relies on a detailed environmental history and antigen-specific testing. This case highlights bagasse-derived insulation as an underrecognized source of exposure in urban environments. As ‘eco-friendly’ materials gain popularity, awareness of potential immunogenic byproducts is essential to ensure sustainability does not come at the expense of respiratory health. This abstract is funded by: None
Araiza et al. (Fri,) studied this question.