Progressive Disease With Low Survival in Adult Patients With Pulmonary Fibrosis Carrying Surfactant-Related Gene Mutations: An Observational Study

Abstract

In some patients with progressive fibrosing interstitial lung disease (ILD), disease is caused by carriage of a mutation in a surfactant-related gene (SRG) such as SFTPC, SFTPA2, or ABCA3. However, no aggregated data on disease evolution and treatment outcome have been presented for these patients. In adult patients with ILD with an SRG mutation, what is the course of lung function after diagnosis and during treatment and the survival in comparison with patients with sporadic idiopathic pulmonary fibrosis (sIPF) and familial pulmonary fibrosis (FPF)? We retrospectively examined the clinical course of a cohort of adults with an SRG mutation by screening 48 patients from 20 families with an SRG mutation for availability of clinical follow-up data. For comparison, 248 patients with FPF and 575 patients with sIPF were included. Twenty-three patients with ILD (median age: 45 years; 11 men) with an SRG mutation fulfilled criteria. At diagnosis, patients with an SRG mutation were younger and less often male, but had lower FVC (72%predicted) and diffusing capacity of the lungs for carbon monoxide (46%predicted) compared with patients with FPF or sIPF. In the SRG mutation group, median FVC decline 6months after diagnosis was -40mL and median transplant-free survival was 44months and not different from patients with FPF or sIPF. FVC course was not different among the three cohorts; however, a significantly larger decrease in FVC was found while patients received immunomodulatory or antifibrotic treatment compared with those receiving no treatment. Subsequent analysis in the SRG group showed that patients with a surfactant mutation (n= 7) treated for 6months with antifibrotic drugs showed stable lung function with a median change in FVC of+40mL (interquartile range, -40 to 90mL), whereas patients with an SRG mutation treated with immunomodulatory drugs showed a variable response dependent on the gene involved. This study showed that patients with ILD carrying an SRG mutation experience progressive loss of lung function with severely reduced survival despite possible beneficial effects of treatment.