Keratosis is keratin production on the skin or mucous membrane that derive from keratinocytes. The living keratinocytes of the deeper epidermis change into the dead corneocytes of the horny layer. A wide range of lesions occur as a result of mutation in the gene coding for the various keratin proteins. The hyperkeratotic form olp also belongs to facultative precancerous disease. The etiology of these diseases has not been investigated yet fully.