Hyperkeratosis (from Ancient Greek: ὑπέρ (hyper, “over”); keratos - keratin) is thickening of the stratum corneum (the outermost layer of the epidermis), often associated with the presence of an abnormal quantity of keratin, and also usually accompanied by an increase in the granular layer. As the corneum layer normally varies greatly in thickness in different sites, some experience is needed to assess minor degrees of hyperkeratosis.
Follicular hyperkeratosis dass (also called "Phrynoderma") is a skin condition characterized by excessive development of keratin in hair follicles, resulting in rough, cone-shaped, elevated papules. The openings are often closed with a white plug of encrusted sebum.
This condition has been shown in several small-scale studies to respond well to supplementation with vitamins and fats rich in essential fatty acids. Some research suggests this is due mainly to E and B vitamins. Vitamin A is also listed as connected to the pathology.
By other specific site
Plantar hyperkeratosis is hyperkeratosis of the sole of the foot. It is recommended to surgically remove the dead skin, to provide symptomatic relief.
Hyperkeratosis of the nipple and areola is an uncommon benign, asymptomatic, acquired condition of unknown pathogenesis.:636
Epidermolytic hyperkeratosis (also known as "Bullous congenital ichthyosiform erythroderma," "Bullous ichthyosiform erythroderma,":482 or "bullous congenital ichthyosiform erythroderma Brocq") is a rare skin disease in the ichthyosis family affecting around 1 in 250,000 people. It involves the clumping of keratin filaments.:562
Keratosis Pilaris appears similar to gooseflesh, is usually asymptomatic and may be treated by moisturizing the skin.
Hyperkeratosis lenticularis perstans (also known as "Flegel's disease") is a cutaneous condition characterized by rough, yellow-brown keratotic, flat-topped papules.:639
Hyperkeratosis of mucous membranes
The term hyperkeratosis is often used in connection with lesions of the mucous membranes, such as leukoplakia. Because of the differences between mucous membranes and the skin (e.g. keratinizing mucosa does not have a stratum lucidum and non keratinizing mucosa does not have this layer or normally a stratum corneum or a stratum granulosum), sometimes specialized texts give slightly different definitions of hyperkeratosis in the context of mucosae. Examples are "an excessive formation of keratin (e.g., as seen in leukoplakia)" and "an increase in the thickness of the keratin layer of the epithelium, or the presence of such a layer in a site where none would normally be expected."
^Nadiger, HA (1980). "Role of vitamin E in the aetiology of phrynoderma (follicular hyperkeratosis) and its interrelationship with B-complex vitamins". The British journal of nutrition44 (3): 211–4. doi:10.1079/bjn19800033. PMID7437404.
^ abcOdom, Richard B.; Davidsohn, Israel; James, William D.; Henry, John Bernard; Berger, Timothy G.; Clinical diagnosis by laboratory methods; Dirk M. Elston (2006). Andrews' diseases of the skin: clinical dermatology. Saunders Elsevier. ISBN0-7216-2921-0.
^ abcRapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN1-4160-2999-0.
^ abFreedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.