The occurrence of pulmonary fibrosis in numerous individuals from the same family suggests a genetic cause for the disease. During the past 10 years, germline mutations involving proteins from the telomerase complex and from the surfactant system have been identified in association with pulmonary fibrosis. Mutations of TERT, the coding gene for the telomerase reverse transcriptase, are the most frequently identified mutations and are present in 15% of cases of familial pulmonary fibrosis. More recently mutations in RTEL1 and PARN have been described in 5–10% of the family, respectively. Other mutations (TERC, surfactant proteins genes) are only rarely evidenced in adults. Patients with mutations involving the telomerase complex may present with pulmonary fibrosis, haematological, cutaneous or hepatic diseases. Evidence for mutations associated with the development of pulmonary fibrosis raises numerous clinical questions from establishing a diagnosis, providing counselling to deciding on therapy, and requires specific studies. From a pathophysiological point of view, the function of the genes highlights the central role of alveolar epithelium and ageing in fibrogenesis.