Keratins are a family of intermediate filament proteins that assemble into filaments through forming heterodimers of one type I keratin (keratins 9 to 23) and one type II keratin (keratins 1 to 8). Keratins demonstrate tissue and differentiation specific expression profiles. Cytokeratin 1 is a hetero-tetramer of two type I as well as two type II keratins, keratin-10 (KRT10). Keratin 1 is differentiation specific keratin that is one of the predominant keratins in suprabasal keratinocytes in stratified epithelia. Mutations in keratin 1 cause epidermolytic hyperkeratosis.