To date, ACD, CTC1, DKC1, NHP2, NOP10, PARN, RTEL1, TERC, TERT, TINF2, and WRAP53 are the genes in which pathogenic variants are known to cause dyskeratosis congenita (DC) and result in very short telomeres (Savage and Alter, 2009). The gene discussed is ACD; the disease is dyskeratosis congenita.