Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin,[Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) Robbins & Cotran Pathologic Basis of Disease (7th ed.). Saunders. Page 1230. .] and is 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.
It can be caused by vitamin A deficiency or chronic exposure to arsenic.
Hyperkeratosis can also be caused by B-Raf inhibitor drugs such as vemurafenib and dabrafenib.[Niezgoda, Anna; Niezgoda, Piotr; Czajkowski, Rafal (2015) Novel Approaches to Treatment of Advanced Melanoma: A Review of Targeted Therapy and Immunotherapy BioMed Research International]
It can be treated with urea-containing creams, which dissolve the intercellular matrix of the cells of the stratum corneum, promoting desquamation of scaly skin, eventually resulting in softening of hyperkeratotic areas.[ drugs.com > Urea Cream (Prescribing Information) Revised: 04/2010 by Stratus Pharmaceuticals]
Types
Follicular
Follicular hyperkeratosis, also known as
keratosis pilaris (KP), is a skin condition characterized by excessive development of
keratin in
, resulting in rough, cone-shaped, elevated
. The openings are often closed with a white plug of encrusted
sebum. When called
phrynoderma, the condition is associated with nutritional deficiency or malnourishment.
This condition has been shown in several small-scale studies to respond well to supplementation with vitamins and fats rich in essential fatty acids. Avitaminosis of vitamin E,
By other specific site
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Plantar hyperkeratosis is hyperkeratosis of the sole of the foot. It is recommended to surgically remove the dead skin, to provide symptomatic relief.
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Hyperkeratosis of the nipple and areola is an uncommon benign, asymptomatic, acquired condition of unknown pathogenesis.
Hereditary
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Epidermolytic hyperkeratosis (also known as "Bullous congenital ichthyosiform erythroderma,"
[Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. .] or "bullous congenital ichthyosiform erythroderma of Brocq"
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Multiple minute digitate hyperkeratosis, a rare cutaneous condition, with about half of cases being familial
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Focal acral hyperkeratosis (also known as "Acrokeratoelastoidosis lichenoides,") is a late-onset keratoderma, inherited as an autosomal dominant condition, characterized by oval or polygonal crateriform developing along the border of the hands, feet, and wrists.
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Keratosis pilaris appears similar to gooseflesh, is usually asymptomatic and may be treated by moisturizing the skin.
Other
-
Hyperkeratosis lenticularis perstans (also known as "Flegel's disease"
In mucous membranes
The term hyperkeratosis is often used in connection with lesions of the
, 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)"
[Mosby's Dental Dictionary] 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."
Etymology and pronunciation
The word
hyperkeratosis () is based on the Ancient Greek morphemes
+ +
, meaning 'the condition of too much keratin'.
Hyperkeratosis in dogs
Nasodigitic hyperkeratosis in dogs may be idiopathic, secondary to an underlying disease, or due to congenital abnormalities in the normal anatomy of the nose and fingertips.
In the case of congenital anatomical abnormalities, contact between the affected area and rubbing surfaces is impaired. It is roughly the same with finger pads — in animals with an anatomical abnormality, part of the pad is not in contact with rubbing surfaces and excessive keratin deposition is formed. The idiopathic form of nasodigitic hyperkeratosis in dogs develops from unknown causes and is more common in older animals (senile form).
Therapy
Since the deposition of excess keratin cannot be stopped, therapy is aimed at softening and removing it. For moderate to severe cases, the affected areas should be hydrated (moisturised) with warm water or compresses for 5-10 minutes. Softening preparations are then applied once a day until the excess keratin is removed.
In dogs with severe hyperkeratosis and a significant excess of keratin, it is removed with scissors or a blade. After proper instructions, pet owners are able to perform this procedure at home, and it may be the only method of correction.
See also
External links
