Phacomatosis pigmentokeratotica is caused by a postzygotic HRAS mutation in a multipotent progenitor cell - Groesser, L; Herschberger, E; Sagrera, A; Shwayder, T; Flux, K; Ehmann, L; Wollenberg, A; Torrelo, A; Bagazgoitia, L; Diaz-Ley, B; Tinschert, S; Oschlies, I; et al. (JOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, 2013)