Hyperkeratosis
Encyclopedia
Hyperkeratosis is thickening of the stratum corneum
Stratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells that lack nuclei and organelles. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress...

, often associated with a qualitative abnormality of the keratin, and also usually accompanied by an increase also 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
Vitamin A deficiency
Vitamin A deficiency is a lack of vitamin A in humans. It is common in developing countries but rarely seen in developed countries. Night blindness is one of the first signs of vitamin A deficiency. Xerophthalmia and complete blindness can also occur since Vitamin A has a major role in...

 or chronic exposure to arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

.

It can be treated with urea-containing cream
Urea-containing cream
A urea -containing cream is a potent keratolytic emollient...

s, which dissolve the intercellular matrix of the cells of the stratum corneum, promoting desquamation
Desquamation
Desquamation , also called skin peeling, is the shedding of the outermost membrane or layer of a tissue, such as the skin.-Skin:Normal, nonpathologic desquamation of the skin occurs when keratinocytes, after moving apically over about 14 days, are individually shed unnoticeably...

 of scaly skin, eventually resulting in softening of hyperkeratotic areas.

Follicular

Follicular hyperkeratosis dass (also called "Phrynoderma") is a skin condition characterized by excessive development of keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

 in hair follicle
Hair follicle
A hair follicle is a skin organ that produces hair. Hair production occurs in phases, including a growth phase , and cessation phase , and a rest phase . Stem cells are principally responsible for the production of hair....

s, 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 acid
Essential fatty acid
Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them...

s. 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
Sole (foot)
The sole is the bottom of the foot.In humans the sole of the foot is anatomically referred to as the plantar aspect. The equivalent surface in ungulates is the hoof.- Human sole :...

 of the foot
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...

. 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.

Hereditary

  • Epidermolytic hyperkeratosis
    Epidermolytic hyperkeratosis
    Epidermolytic hyperkeratosis, is a rare skin disease in the ichthyosis family affecting around 1 in 250,000 people.It involves the clumping of keratin filaments.-Presentation:At birth, affected babies are called "enfant...

     (also known as "Bullous congenital ichthyosiform erythroderma," "Bullous ichthyosiform erythroderma," or "bullous congenital ichthyosiform erythroderma Brocq") is a rare skin disease in the ichthyosis
    Ichthyosis
    Ichthyosis is a heterogeneous family of at least 28, generalized, mostly genetic skin disorders. All types of ichthyosis have dry, thickened, scaly or flaky skin...

     family affecting around 1 in 250,000 people. It involves the clumping of keratin
    Keratin
    Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

     filaments.
  • Multiple minute digitate hyperkeratosis
    Multiple minute digitate hyperkeratosis
    Multiple minute digitate hyperkeratosis is a rare cutaneous condition, with about half of cases being familial, inherited in an autosomal dominant fashion, while the other half are sporadic.This disease has a unique histology, so a...

    , a rare cutaneous condition, with about half of cases being familial
  • Focal acral hyperkeratosis
    Focal acral hyperkeratosis
    Focal acral hyperkeratosis is a late-onset keratoderma, inherited as an autosomal dominant condition, characterized by oval or polygonal crateriform papules developing along the border of the hands, feet, and wrists.It is considered similar to Costa acrokeratoelastoidosis.-See...

     (also known as "Acrokeratoelastoidosis lichenoides,") is a late-onset keratoderma
    Keratoderma
    -Congenital:* Simple keratodermas** Diffuse palmoplantar keratodermas*** Diffuse epidermolytic palmoplantar keratoderma*** Diffuse nonepidermolytic palmoplantar keratoderma*** mal de Meleda** Focal palmoplantar keratoderma*** Striate palmoplantar keratoderma...

    , inherited as an autosomal dominant condition, characterized by oval or polygonal crateriform papule
    Papule
    A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm,...

    s developing along the border of the hands, feet, and wrists.

Other

  • Hyperkeratosis lenticularis perstans (also known as "Flegel's disease") is a cutaneous condition characterized by rough, yellow-brown keratotic, flat-topped papule
    Papule
    A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm,...

    s.

See also

  • Skin lesion
  • Skin disease
  • Keratin disease
    Keratin disease
    A keratin disease is a genetic disorder of one of the keratin genes.An example is monilethrix.The first to be identified was epidermolysis bullosa simplex.Examples include:-References:...

  • List of skin diseases
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