Antigen avoidance and environmental inhalation challenge for successful diagnosis of fibrotic hypersensitivity pneumonitis mimicking idiopathic pulmonary fibrosis

• Published in: Respiratory medicine case reports 2022-01, Vol.39, p.101737, Article 101737
• Main Authors: Ito, Yasuhiro, Miwa, Seiichi, Hayakawa, Hiroshi, Oshima, Tomoko, Eihuku, Tatsuru, Iwaizumi, Eriko, Ohba, Hisano, Fujita, Kaoru, Kanai, Miho, Shirai, Masahiro
• Format: Article
• Language: English
• Subjects: Antigen avoidance; Case Report; Farmer's lung; Fibrotic hypersensitivity pneumonitis; Idiopathic pulmonary fibrosis; Inhalation challenge
• ISSN: 2213-0071; 2213-0071
• DOI: 10.1016/j.rmcr.2022.101737

A 77-year-old man was initially diagnosed with idiopathic pulmonary fibrosis (IPF) and treated with anti-fibrotic nintedanib. Despite undergoing anti-fibrotic treatment for one year, his condition remained unstable. The patient was admitted to our hospital for exertional dyspnea. We performed an exposure assessment, including 2-week antigen avoidance and an environmental inhalation challenge, and successfully re-diagnosed him with fibrotic hypersensitivity pneumonitis (HP), known as chronic farmer's lung. Adding oral glucocorticoids to the nintedanib treatment improved his condition. Although antigen avoidance and environmental inhalation challenge tests are not standardized, they may be useful for diagnosing fibrotic HP when properly applied. •Clinical features of fibrotic HP and IPF are often indistinguishable.•Antigen avoidance is crucial in the diagnosis and management of fibrotic HP.•Environmental inhalation challenge is useful when applied properly.•The seasonal change of clinical parameters helps suspecting fibrotic HP.