CK20, or Keratin 20, type I, is a human gene encoded by KRT20. It may also be known as: Keratin, type I cytoskeletal 20; Cytokeratin-20; CK-20; Keratin-20; K20; Protein IT; KRT21. The encoded protein has an amino acid length of 424 and a mass of 48.5 kDa. Other isoforms may exist. CK20 is a member of the Intermediate filament family. Homologs of this gene exist in other organisms, including: Mouse, Chicken.