Rationale: Familial clustering of adult idiopathic interstitial pneumonias (IIP) suggests that genetic factors might play an important role in disease development. Mutations in the gene encoding surfactant protein C (SFTPC) have been found in children and families with idiopathic pneumonias, whereas cocarriage of a mutation in ATP-binding cassette subfamily A member 3 (ABCA3) was postulated to have a disease-modifying effect.
Objectives: To investigate the contribution of SFTPC mutations to adult familial pulmonary fibrosis (FPF) and the disease-modifying effect of mutations in ABCA3 within their families.
Methods: Twenty-two unrelated patients with FPF (10%) were identified within our single-center cohort of 229 patients with IIP. SFTPC was sequenced in 20 patients with FPF and 20 patients with sporadic IIP. In patients with an SFTPC mutation, sequencing of ABCA3 was performed. Discovered variants were typed in more than 100 control subjects and 121 additional patients with sporadic IIP.
Measurements and main results: In 5/20 unrelated patients with FPF (25%; confidence interval, 10-49) a mutation in SFTPC was detected: M71V, IVS4+2, and three times I73T. No mutations were detected in the sporadic or control cohort. Patients with SFTPC mutations presented with a histopathological pattern of usual interstitial pneumonia and nodular septa thickening and multiple lung cysts in combination with ground glass or diffuse lung involvement on chest high-resolution computed tomography. Two variants in ABCA3 were found in adult patients with FPF but not in affected children.
Conclusions: Mutations in SFTPC are a frequent cause of FPF in adult patients in our cohort. Nonclassifiable radiological patterns with cystic changes and histopathological patterns of usual interstitial pneumonia are characteristics of adult SFTPC mutation carriers.