KRT6C and pachyonychia congenita: In humans, the KRT6 family includes a third member (KRT6C, encoding K6c), mutations in which have been associated with a milder form of PC with no/minor nail defects (PC-K6c) that was initially reported as palmoplantar keratoderma, non-epidermolytic, focal or diffuse (PPKNEFD, OMIM #615735).