Curiously, inboth the K17−/− and TGM3−/− mice there is no nail defect despite both genes being expressed in the nail bed, even though missense mutations in keratin17 are related to type 2 pachyonychia congenita, which presents with severe nail dystrophy [44] and pili torti[46]. Here, KRT17 is linked to pachyonychia congenita.