- Missense mutations in keratin 17 cause either pachyonychia congenita type 2 or a phenotype resembling steatocystoma multiplex. Smith, F.J., Corden, L.D., Rugg, E.L., Ratnavel, R., Leigh, I.M., Moss, C., Tidman, M.J., Hohl, D., Huber, M., Kunkeler, L., Munro, C.S., Lane, E.B., McLean, W.H. J. Invest. Dermatol. (1997)