Palmoplantar Keratoderma, Nonepidermolytic, Focal or Diffuse, also known as ppknefd, is related to median rhomboid glossitis and white sponge nevus. An important gene associated with Palmoplantar Keratoderma, Nonepidermolytic, Focal or Diffuse is KRT6C (Keratin 6C), and among its related pathways/superpathways are Nervous system development and COPI-independent Golgi-to-ER retrograde traffic. Affiliated tissues include skin, and related phenotypes are oral leukoplakia and palmoplantar keratoderma