Contribution of mutations in genes of the surfactant system to idiopathic interstitial pneumonia (IIP)

Background: Children and adult IIP are heterogeneous and severe disorders. Whereas telomerase gene mutations are preferentially found in adult IIP, surfactant gene mutations are mainly reported in children. The study aimed to assess the contribution of surfactant gene mutations in a large pediatric and adult IIP cohort. Methods: Patients with IIP were prospectively included in the French network of rare lung diseases centres. All SFTPA1, SFTPA2, SFTPB, SFTPC, ABCA3, NKX2-1 exons and flanking intronic sequences were analyzed. The identified variations were assessed in silico. Only pathogenic or likely pathogenic mutations were taken into account. Results: 477 patients were included in 4 years (190 children; 287 adults). The mean age at diagnosis was 40 years (0-100) and the sex ratio was 1.47 M/F. The IIP was familial in 22% of cases. A personal or family history of lung cancer was found in 44 (15%) adults. A mutation was identified in a surfactant gene in 45 (9.4%) patients, including 22 (11.6%) children and 23 (8%) adults. Mutations were identified in all the studied genes in children and in adults, except for a SFTPB mutation identified in an adult. A mutation was found in 25% of the 44 adults with a history of IIP and lung cancer (SFTPA = 10, SFTPC = 1). Discussion and conclusion: Surfactant gene mutations encounter for an important part of IIP, thereby strongly suggesting that these molecular analyses should be part of the diagnosis process of IIP, regardless of the patient’s age, especially in case of family history of IIP and/or lung cancer. Such systematic approach should help guiding the most relevant genetic tests to be performed according to the disease phenotype.