A familial history of pulmonary fibrosis in patients with chronic hypersensitivity pneumonitis.

BACKGROUND Hypersensitivity pneumonitis (HP) is an immunologically mediated lung disease induced by the inhalation of a variety of antigens. Patients with chronic HP often have a family history of pulmonary fibrosis. This strongly suggests that both genetic and environmental factors play an important role in the pathogenesis of chronic HP. OBJECTIVES We aimed to investigate the epidemiology and clinical features of chronic HP patients with a family history of pulmonary fibrosis. METHODS We retrospectively reviewed the clinical information of 114 cases diagnosed with chronic HP with insidious onset between 1992 and 2009. RESULTS Twenty cases (17.5%) were identified as having a family history of pulmonary fibrosis. All of these patients had lived apart from their afflicted relatives for at least several decades. The familial cases were younger than the nonfamilial cases at onset (57.5 ± 9.6 vs. 64.0 ± 7.0 years old, p = 0.008). The predicted vital capacity percentage and partial pressure of oxygen in arterial blood gas were significantly higher in the familial cases. There were no differences between the 2 groups in gender, smoking history, bronchoalveolar lavage fluid profile, radiologic findings or other clinical features. CONCLUSIONS We found a familial clustering in patients with chronic HP. Various factors including genetic susceptibility to pulmonary fibrosis and environmental factors may contribute to the development of familial chronic HP.