Clustering of lung diseases in the family of interstitial lung disease patients.

BACKGROUND: The presence of familial interstitial lung disease (ILD) has been found to predict development of progressive pulmonary fibrosis. However, the role of non-ILD lung diseases in ILD patients' families has not yet been investigated. We aimed to identify associations between ILDs and non-ILD lung diseases from ILD patients' self-reported family health history. METHODS: We analysed questionnaires on family health history of 1164 ILD patients for the occurrence of ILD and non-ILD lung disease in relatives. Logistic regression analysis was used to study associations with diagnosis groups. RESULTS: Familial pulmonary fibrosis was reported by 20% of patients with idiopathic pulmonary fibrosis (IPF; OR 9.2, 95% CI 4.7-17.9), and 15% of patients with unclassifiable pulmonary fibrosis (OR 4.1, 95% CI 2.0-8.2). Familial occurrence was reported by 14% of patients with sarcoidosis (OR 3.3, 95% CI 1.9-5.8). Regarding non-ILD lung disease, significantly more patients with IPF (36%) reported lung cancer in their family (OR 2.3, 95% CI 1.4-3.5), and patients with hypersensitivity pneumonitis (18%) mostly reported COPD (OR 2.3, 95% CI 1.3-4.2). Comparison of sporadic and familial ILD patients' reports showed that emphysema (OR 4.6, 95% CI 1.8-11.6), and lung cancer (OR 2.4, 95% CI 1.2-4.9) were predictive for familial pulmonary fibrosis, particularly when reported both in a family (OR 16.7, 95% CI 3.2-86.6; p < 0.001). CONCLUSIONS: Our findings provide evidence for clustering of ILD and non-ILD lung diseases in families and show that self-reported emphysema and lung cancer of relatives in this population predicts familial pulmonary fibrosis.