Dyskeratosis congenita (DC), a telomere biology disorder, is characterized by a classic triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia. However, the classic triad may not be present in all individuals. People with DC are at increased risk for progressive bone marrow failure (BMF), myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML), solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Other findings can include: abnormal pigmentation changes not restricted to the upper chest and neck, eye abnormalities (epiphora, blepharitis, sparse eyelashes, ectropion, entropion, trichiasis), and dental abnormalities (caries, periodontal disease, taurodauntism). Although most persons with DC have normal psychomotor development and normal neurologic function, significant developmental delay is present in the two variants in which additional findings include cerebellar hypoplasia (Hoyeraal Hreidarsson syndrome) and bilateral exudative retinopathy and intracranial calcifications (Revesz syndrome). Onset and progression of manifestations of DC vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF.
All individuals with DC have abnormally short telomeres for their age, as determined by multicolor flow cytometry fluorescence in situ hybridization (flow-FISH) on white blood cell (WBC) subsets. To date, CTC1, DKC1, TERC, TERT, TINF2, NHP2, NOP10, and WRAP53 are the genes in which mutations are known to cause DC and result in very short telomeres. Mutations in one of these eight genes have been identified in approximately half of individuals who meet clinical diagnostic criteria for DC. Molecular genetic testing is available clinically for seven of these genes.
The mode of inheritance of DC varies by gene: DKC1 (X-linked), TERC and TINF2 (autosomal dominant), TERT (autosomal dominant or autosomal recessive), CTC1, WRAP53, NHP2, and NOP10 (autosomal recessive). Genetic counseling regarding risk to family members depends on accurate diagnosis, determination of the mode of inheritance in each family, and results of molecular genetic testing. Prenatal testing for pregnancies at increased risk may be possible for DC if the disease-causing mutation(s) in the family is/are known.