Hypersensitivity pneumonitis secondary to foam exposure in mattress and pillows.

Fibrotic hypersensitivity pneumonitis (HP) has a poor prognosis when no antigen is identified, which occurs in many cases. We present a case of HP due to foam exposure in bedding, an unrecognised cause of HP. A woman was referred for dyspnoea and cough. High-resolution chest computed tomography (HRCT) showed a three-density pattern with gas trapping. Pulmonary function tests (PFTs) revealed restriction and reduced diffusing capacity. Bronchoalveolar lavage showed lymphocytosis (43%) and lung cryobiopsy showed fibrosis, lymphocytic infiltration and multinucleated giant cells. She had foam in mattress and pillows but no other exposures. Her symptoms, PFTs, and imaging improved after avoiding foam in her bedding. After re-exposure to a foam pillow, her symptoms, PFTs, and HRCT worsened. Microbiological analysis of the foam pillow reported , known to cause HP. Foam exposure is a novel cause of HP, and foam avoidance can prevent disease progression and death.