Knuckle pads, in an epidermal palmoplantar keratoderma patient with Keratin 9 R163W transgrediens expression.

Epidermolytic PalmoPlantar keratoderma (EPPK) Vörner-type is an autosomal dominantly inherited skin disease, characterized by severe thickening of the palms and soles, caused by mutations in the keratin K9 (KRT9) gene. To date, a number of KRT9 mutations have been detected, most of which affect the highly conserved 1A region of the central alpha-helical domain, important for keratin heterodimerization. The most common mutation is the substitution of the arginine in position 163 with a tryptophan (R163W), which has been reported in North American, European, and Japanese populations.