a group of noninflammatory diseases of the skin of varied origins whose common manifestation is thickening of the horny layer. The development of keratosis is caused either by hyperplasia (intensified growth) of the horny layer or by increased cohesiveness (knitting) of the cells of that layer; with keratosis the sloughing of scales occurs five to ten times more slowly than in normal skin.

A distinction is made between congenital keratoses, which are due to congenital defects in the processes of cornification (ichthyosis and keratoderma), and acquired keratoses, which arise with various generalized and localized pathological processes (callosity, hypovitaminosis, and endocrine, toxic, syphilitic, gonorrheal, and other processes). Another form are the constitutional keratoses (lichen pilaris and kerosis), which form as a result of the effects of partly congenital and partly acquired unfavorable factors. Treatment of keratoses depends on the causes that produced development of the process.