A 48-year-old man presented to our hospital because of diarrhea and severe renal dysfunction. Laboratory examination revealed pancytopenia, which deteriorated gradually. He was diagnosed with dyskeratosis congenita (DKC) by genetic screening. At the age of 50, the patient was referred to the Department of Respiratory Medicine because of repeated dry cough. Chest X ray and high-resolution computed tomography revealed bilateral pulmonary reticular shadows which indicated interstitial pneumonia; however, he refused further examination. At the age of 52, the interstitial pneumonia exacerbated rapidly, and he died of respiratory failure 6 days later. To elucidate the cause of death, autopsy was performed. The autopsy findings showed diffuse pulmonary fibrosis, probably due to the difference in mechanisms of fibrosis between idiopathic pulmonary fibrosis and DKC. Clinicians must bear in mind that some of the patients diagnosed with idiopathic pulmonary fibrosis may have genetic abnormalities, as in this case