Dyskeratosis Congenita Complicated by Pulmonary Fibrosis and Myelodysplastic Syndrome with a Germline Mutation of the <i>DKC1</i> Gene and a Somatic Mutation of the <i>U2AF1</i> Gene in Leukocytes

Dyskeratosis congenita (DC) is a rare genetic disorder that is caused by abnormal telomere shortening. We herein report the case of a 40-year-old man with classic DC characterized by a mucocutaneous triad complicated by pulmonary fibrosis and myelodysplastic syndrome (MDS). The telomere length of lymphocytes was extremely short (-3.3 standard deviations). We identified the germline mutation c.C91A in DKC1 gene. We also identified a somatic mutation c.C101T in the U2AF1 gene of leukocytes, which may be associated with MDS development. Nintedanib was started, but the patient died of bilateral pneumothorax 6 months after diagnosis.