Genetics of the Combined Pulmonary Fibrosis and Emphysema Syndrome

The combined pulmonary fibrosis and emphysema syndrome (CPFE) individualized by our group in 2005 is characterized by an often severe dyspnea, almost exclusive male predominance, and often major, profound impairment of gas exchange contrasting with preserved lung volumes and absence of airflow obstruction, and a high risk of pre-capillary pulmonary hypertension responsible for increased mortality. Almost all patients are smokers or ex-smokers. There are some arguments in favor of genetic abnormalities in this syndrome of unknown etiology (other than smoking) including short telomeres and mutations in the telomerase complex genes. There are also emphysematous lesions, in patients with familial pulmonary fibrosis, with mutations in the SFTPC gene (surfactant protein C), and reported cases of CPFE syndrome with SFTPC mutation. No large genetic studies have been conducted to date in the CPFE syndrome. Our main hypothesis is that the proportion of subjects with short telomeres is higher among patients with CPFE syndrome than in subjects of similar age with idiopathic pulmonary fibrosis but without emphysema. It has previously been shown that mutations in the telomerase TERT or TERC genes are mostly found in people whose telomeres are abnormally short. The investigators propose to use that test to identify patients most likely carrying a mutation, and to seek, among them, the mutations in the TERT or TERC telomerase genes. The objective of the study is to compare the proportion of patients with short telomeres in the group of patients with CPFE syndrome to that of other patients (with idiopathic pulmonary fibrosis without emphysema, or with emphysema without fibrosis).