Dyskeratosis congenita (DC) is a rare inherited multisystem disorder caused by mutations in seven genes involved in telomere biology, with approximately 20% of cases having pulmonary complications. DKC1 mutations exhibit a severe disease phenotype of DC that develops in early childhood. Here, we report a unique case of DC with pulmonary fibrosis diagnosed at the age of 46. A novel missense mutation(p.Arg65Lys) of DKC1 was detected, and predicted to show a weak mutagenic effect. In spite of the steroid and immunosuppressive treatment, he died of an acute exacerbation seven months after the initial visit. This case suggests that mutation subtypes can cause heterogeneity in DC and pulmonary fibrosis.