Investigations on families have identified genetic variants in SFTPC (encoding surfactant protein C), SFTPA2 (encoding surfactant protein A2), MUC5B (encoding a mucin constituent of the mucus), as well as TERT and TERC (encoding components of the telomerase complex) to be associated with pulmonary fibrosis (Nogee et al., 2001; Thomas et al., 2002; Armanios et al., 2007; Tsakiri et al., 2007; Wang et al., 2009; van Moorsel et al., 2010; Ono et al., 2011; Seibold et al., 2011). Here, MUC5B is linked to pulmonary fibrosis.