Dyskeratosis congenita: An inherited cause of bone-marrow failure, dyskeratosis congenita is a syndrome characterized by abnormal excess skin pigmentation, abnormal or absent nails, and mucosal leukoplakia (white premalignant areas on the lips and conjunctiva of the eyes and in the mouth, anus, and urethra).
Most cases of the disease are X-linked. They are due to mutations (changes) in a gene on the X chromosome called DKC1 which encodes a protein called dyskerin. A seemingly-normal mother carrying the DKC1 mutation has a 50:50 chance of transmitting it to a son who then will suffer from the disease. The average age at death is 24 years.