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Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands.[1] The major function of this system is as a barrier against the external environment.[2] The skin weighs an average of four kilograms, covers an area of two square metres, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue.[1] The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin.[3] Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle.[4] In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.[5][6][7]

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Rash due to measles

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.[8] Nourishment is provided to these layers by diffusion from the dermis since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis.[3] This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface.[3] In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.[9]

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis.[10] The superficial papillary dermis interdigitates with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone.[10] Structural components of the dermis are collagen, elastic fibers, and ground substance.[10] Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands.[8] The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels.[8][11] The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.[12][13]

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia.[14] This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus.[3] The main cellular component of this tissue is the adipocyte, or fat cell.[14] The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance.[8] Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.[14]

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails).[15][16] While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described.[14] Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known.[17][18] Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on.[19][20] Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow).[21] Diagnosis of many conditions often also requires a skin biopsy which yields histologic information[22][23] that can be correlated with the clinical presentation and any laboratory data.[24][25][26]

Acneiform eruptions

See also: Category:Acneiform eruptions
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Acne vulgaris
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Dissecting cellulitis of the scalp
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Rhinophyma

Acneiform eruptions are caused by changes in the pilosebaceous unit.[27][28]

Autoinflammatory syndromes

See also: Category:Autoinflammatory syndromes

Autoinflammatory syndromes are a group of inherited disorders characterized by bouts of inflammatory skin lesions and periodic fevers.[29][30]

Chronic blistering

See also: Category:Chronic blistering cutaneous conditions

Chronic blistering cutaneous conditions have a prolonged course and present with vesicles and bullae.[31][32][33]

Conditions of the mucous membranes

See also: Category:Conditions of the mucous membranes

Conditions of the mucous membranes involve the moist linings of the eyes, nose, mouth, genitals, and anus.[34]

Conditions of the skin appendages

See also: Category:Conditions of the skin appendages

Conditions of the skin appendages are those affecting the glands of the skin, hair, nails, and arrector pili muscles.[1][35]

Conditions of the subcutaneous fat

See also: Category:Conditions of the subcutaneous fat

Conditions of the subcutaneous fat are those affecting the layer of adipose tissue that lies between the dermis and underlying fascia.[36][37][38][39]

Congenital anomalies

See also: Category:Cutaneous congenital anomalies

Cutaneous congenital anomalies are a diverse group of disorders that result from faulty morphogenesis, the biological process that forms the shape of a human body.[35][40][41]

Connective tissue diseases

See also: Category:Connective tissue diseases

Connective tissue diseases are caused by a complex array of autoimmune responses that target or affect collagen or ground substance.[35][43]

Abnormalities of dermal fibrous and elastic tissue

See also: Category:Abnormalities of dermal fibrous and elastic tissue
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Striae distensae

Abnormalities of dermal fibrous and elastic tissue are caused by problems in the regulation of collagen synthesis or degradation.[35][44]

Dermal and subcutaneous growths

See also: Category:Dermal and subcutaneous growths

Dermal and subcutaneous growths result from (1) reactive or neoplastic proliferation of cellular components of the dermis or subcutaneous tissue, or (2) neoplasms invading or aberrantly present in the dermis.[1][35]

Dermatitis

See also: Category:Dermatitis

Dermatitis is a general term for "inflammation of the skin".[45]

Atopic

See also: Category:Atopic dermatitis

Atopic dermatitis is a chronic dermatitis associated with a hereditary tendency to develop allergies to food and inhalant substances.[46][47][48]

  • Atopic dermatitis (atopic eczema, disseminated neurodermatitis, flexural eczema, infantile eczema, prurigo diathsique)

Contact

See also: Category:Contact dermatitis

Contact dermatitis is caused by certain substances coming in contact with the skin.[49][50][51]

Eczema

See also: Category:Eczema

Eczema refers to a broad range of conditions that begin as spongiotic dermatitis and may progress to a lichenified stage.[26][52]

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Dyshidrosis

Pustular

See also: Category:Pustular dermatitis

Pustular dermatitis is an inflammation of the skin that presents with pustular lesions.[26][53]

Seborrheic

See also: Category:Seborrheic dermatitis

Seborrheic dermatitis is a chronic, superficial, inflammatory disease characterized by scaling on an erythematous base.[54]

Disturbances of pigmentation

See also: Category:Disturbances of human pigmentation

Disturbances of human pigmentation, either loss or reduction, may be related to loss of melanocytes or the inability of melanocytes to produce melanin or transport melanosomes correctly.[55][56][57]

Drug eruptions

See also: Category:Drug eruptions

Drug eruptions are adverse drug reactions that present with cutaneous manifestations.[58][59][60]

Endocrine-related

See also: Category:Endocrine-related cutaneous conditions

Endocrine conditions often present with cutaneous findings as the skin interacts with the endocrine system in many ways.[61][62]

Eosinophilic

See also: Category:Eosinophilic cutaneous conditions

Eosinophilic cutaneous conditions encompass a wide variety of diseases that are characterized histologically by the presence of eosinophils in the inflammatory infiltrate, or evidence of eosinophil degranulation.[63][64]

Epidermal nevi, neoplasms, and cysts

See also: Category:Epidermal nevi, neoplasms, and cysts

Epidermal nevi, neoplasms, and cysts are skin lesions that develop from the epidermal layer of the skin.[8][26]

Erythemas

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Erythema migrans
See also: Category:Erythemas

Erythemas are reactive skin conditions in which there is blanchable redness.[1][9]

Genodermatoses

See also: Category:Genodermatoses

Genodermatoses are inherited genetic skin conditions often grouped into three categories: chromosomal, single gene, and polygenetic.[67][68]

Infection-related

See also: Category:Infection-related cutaneous conditions and Skin and skin structure infection

Infection-related cutaneous conditions may be caused by bacteria, fungi, yeast, viruses, or parasites.[26][69]

See also: Category:Bacterium-related cutaneous conditions and Bacterial skin infection

Bacterium-related cutaneous conditions often have distinct morphologic characteristics that may be an indication of a generalized systemic process or simply an isolated superficial infection.[69][70]

See also: Category:Mycobacterium-related cutaneous conditions

Mycobacterium-related cutaneous conditions are caused by Mycobacterium infections.[69][71]

See also: Category:Mycosis-related cutaneous conditions and Fungal skin infection

Mycosis-related cutaneous conditions are caused by fungi or yeasts, and may present as either a superficial or deep infection of the skin, hair, or nails.[69]

Parasitic infestations, stings, and bites

See also: Category:Parasitic infestations, stings, and bites of the skin

Parasitic infestations, stings, and bites in humans are caused by several groups of organisms belonging to the following phyla: Annelida, Arthropoda, Bryozoa, Chordata, Cnidaria, Cyanobacteria, Echinodermata, Nemathelminthes, Platyhelminthes, and Protozoa.[69][72]

See also: Category:Virus-related cutaneous conditions and Viral skin infections

Virus-related cutaneous conditions are caused by two main groups of viruses–DNA and RNA types–both of which are obligatory intracellular parasites.[69][73]

Lichenoid eruptions

See also: Category:Lichenoid eruptions

Lichenoid eruptions are dermatoses related to the unique, common inflammatory disorder lichen planus, which affects the skin, mucous membranes, nails, and hair.[74][75][76]

Lymphoid-related

See also: Category:Lymphoid-related cutaneous conditions

Lymphoid-related cutaneous conditions are a group of disorders characterized by collections of lymphocyte cells within the skin.[77]

Melanocytic nevi and neoplasms

See also: Category:Melanocytic nevi and neoplasms

Melanocytic nevi and neoplasms are caused by either a proliferation of (1) melanocytes, or (2) nevus cells, a form of melanocyte that lack dendritic processes.[78][79]

Melanoma

See also: Category:Melanoma

Melanoma is a malignant proliferation of melanocytes and the most aggressive type of skin cancer.[80][81][82]

Monocyte- and macrophage-related

See also: Category:Monocyte- and macrophage-related cutaneous conditions

Monocyte- and macrophage-related cutaneous conditions are characterized histologically by infiltration of the skin by monocyte or macrophage cells,[10] often divided into several categories, including granulomatous disease,[83] histiocytoses,[84] and sarcoidosis.[85]

Mucinoses

See also: Category:Mucinoses

Mucinoses are a group of conditions caused by dermal fibroblasts producing abnormally large amounts of mucopolysaccharides.[34]

Neurocutaneous

See also: Category:Neurocutaneous conditions

Neurocutaneous conditions are due organic nervous system disease or are psychiatric in etiology.[86][87]

Noninfectious immunodeficiency-related

See also: Category:Noninfectious immunodeficiency-related cutaneous conditions

Noninfectious immunodeficiency-related cutaneous conditions are caused by T-cell or B-cell dysfunction.[88][89]

Nutrition-related

See also: Category:Malnutrition

Nutrition-related cutaneous conditions are caused by malnutrition due to an improper or inadequate diet.[90][91]

Papulosquamous hyperkeratotic

See also: Category:Papulosquamous hyperkeratotic cutaneous conditions

Papulosquamous hyperkeratotic cutaneous conditions are those that present with papules and scales caused by a thickening of the stratum corneum.[9]

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Pityriasis rosea

Palmoplantar keratodermas

See also: Category:Palmoplantar keratodermas

Palmoplantar keratodermas are a diverse group of hereditary and acquired keratodermas in which there is hyperkeratosis of the skin of the palms and soles.[92]

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Palmoplantar keratoderma
  • Acrokeratoelastoidosis of Costa (keratoelastoidosis marginalis)
  • Aquagenic keratoderma (acquired aquagenic palmoplantar keratoderma, aquagenic syringeal acrokeratoderma, aquagenic wrinkling of the palms, transient reactive papulotranslucent acrokeratoderma)
  • Bart–Pumphrey syndrome (palmoplantar keratoderma with knuckle pads and leukonychia and deafness)
  • Camisa disease
  • Carvajal syndrome (striate palmoplantar keratoderma with woolly hair and cardiomyopathy, striate palmoplantar keratoderma with woolly hair and left ventricular dilated cardiomyopathy)
  • Corneodermatoosseous syndrome (CDO syndrome)
  • Diffuse epidermolytic palmoplantar keratoderma (palmoplantar keratoderma cum degeneratione granulosa Vörner, Vörner's epidermolytic palmoplantar keratoderma, Vörner keratoderma)
  • Diffuse nonepidermolytic palmoplantar keratoderma (diffuse orthohyperkeratotic keratoderma, hereditary palmoplantar keratoderma, keratosis extremitatum progrediens, keratosis palmoplantaris diffusa circumscripta, tylosis, Unna–Thost disease, Unna–Thost keratoderma)
  • Erythrokeratodermia variabilis (erythrokeratodermia figurata variabilis, keratosis extremitatum progrediens, keratosis palmoplantaris transgrediens et progrediens, Mendes da Costa syndrome, Mendes da Costa type erythrokeratodermia, progressive symmetric erythrokeratoderma)
  • Focal acral hyperkeratosis (acrokeratoelastoidosis lichenoides, degenerative collagenous plaques of the hand)
  • Focal palmoplantar and gingival keratosis
  • Focal palmoplantar keratoderma with oral mucosal hyperkeratosis (focal epidermolytic palmoplantar keratoderma, hereditary painful callosities, hereditary painful callosity syndrome, keratosis follicularis, keratosis palmoplantaris nummularis, nummular epidermolytic palmoplantar keratoderma)
  • Haim–Munk syndrome (palmoplantar keratoderma with periodontitis and arachnodactyly and acro-osteolysis)
  • Hidrotic ectodermal dysplasia (alopecia congenita with keratosis palmoplantaris, Clouston syndrome, Clouston's hidrotic ectodermal dysplasia, Fischer–Jacobsen–Clouston syndrome, keratosis palmaris with drumstick fingers, palmoplantar keratoderma and clubbing)
  • Howel–Evans syndrome (familial keratoderma with carcinoma of the esophagus, focal non-epidermolytic palmoplantar keratoderma with carcinoma of the esophagus, palmoplantar ectodermal dysplasia type III, palmoplantar keratoderma associated with esophageal cancer, tylosis, tylosis–esophageal carcinoma)
  • Hystrix-like ichthyosis–deafness syndrome (HID syndrome)
  • Keratoderma climactericum (acquired plantar keratoderma, climacteric keratoderma, Haxthausen's disease)
  • Keratosis punctata palmaris et plantaris (Buschke–Fischer–Brauer disease, Davis Colley disease, keratoderma disseminatum palmaris et plantaris, keratosis papulosa, keratoderma punctatum, keratodermia punctata, keratoma hereditarium dissipatum palmare et plantare, palmar and plantar seed dermatoses, palmar keratoses, papulotranslucent acrokeratoderma, punctate keratoderma, punctate keratoses of the palms and soles, maculosa disseminata)
  • Keratitis–ichthyosis–deafness syndrome (erythrokeratodermia progressiva Burns, ichthyosiform erythroderma with corneal involvement and deafness, KID syndrome)
  • Mal de Meleda (acral keratoderma, Gamborg–Nielsen keratoderma, mutilating palmoplantar keratoderma of the Gamborg–Nielsen type, palmoplantar ectodermal dysplasia type VIII, palmoplantar keratoderma of the Norrbotten type)
  • Naxos syndrome (diffuse non-epidermolytic palmoplantar keratoderma with woolly hair and cardiomyopathy, diffuse palmoplantar keratoderma with woolly hair and arrythmogenic right ventricular cardiomyopathy of Naxos, Naxos disease)
  • Olmsted syndrome (mutilating palmoplantar keratoderma with periorificial keratotic plaques, mutilating palmoplantar keratoderma with periorificial plaques, polykeratosis of Touraine)
  • Pachyonychia congenita type I (Jadassohn–Lewandowsky syndrome)
  • Pachyonychia congenita type II (Jackson–Lawler pachyonychia congenita, Jackson–Sertoli syndrome)
  • Palmoplantar keratoderma and spastic paraplegia (Charcot–Marie–Tooth disease with palmoplantar keratoderma and nail dystrophy)
  • Palmoplantar keratoderma of Sybert (Greither palmoplantar keratoderma, Greither syndrome, keratosis extremitatum hereditaria progrediens, keratosis palmoplantaris transgrediens et progrediens, Sybert keratoderma, transgrediens and progrediens palmoplantar keratoderma)
  • Papillon–Lefèvre syndrome (palmoplantar keratoderma with periodontitis)
  • Porokeratosis plantaris discreta
  • Punctate palmoplantar keratoderma
  • Schöpf–Schulz–Passarge syndrome (eyelid cysts with palmoplantar keratoderma and hypodontia and hypotrichosis)
  • Scleroatrophic syndrome of Huriez (Huriez syndrome, palmoplantar keratoderma with scleroatrophy, palmoplantar keratoderma with sclerodactyly, scleroatrophic and keratotic dermatosis of the limbs, sclerotylosis)
  • Striate palmoplantar keratoderma (acral keratoderma, Brünauer–Fuhs–Siemens type of palmoplantar keratoderma, focal non-epidermolytic palmoplantar keratoderma, keratosis palmoplantaris varians, palmoplantar keratoderma areata, palmoplantar keratoderma striata, Wachter keratoderma, Wachters palmoplantar keratoderma)
  • Spiny keratoderma (porokeratosis punctata palmaris et plantaris, punctate keratoderma, punctate porokeratosis of the palms and soles)
  • Tyrosinemia type II (oculocutaneous tyrosinemia, Richner–Hanhart syndrome)
  • Vohwinkel syndrome (keratoderma hereditaria mutilans, keratoma hereditaria mutilans, mutilating keratoderma of Vohwinkel, mutilating palmoplantar keratoderma)

Pregnancy-related

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Linea nigra
See also: Category:Pregnancy-related cutaneous conditions

Pregnancy-related cutaneous conditions are a group of skin changes observed during pregnancy.[93][94]

Pruritic

See also: Category:Pruritic skin conditions

Pruritus, commonly known as itchiness, is a sensation exclusive to the skin, and characteristic of many skin conditions.[95][96]

Psoriasis

See also: Category:Psoriasis

Psoriasis is a common, chronic, and recurrent inflammatory disease of the skin characterized by circumscribed, erythematous, dry, scaling plaques.[97][98][99]

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Psoriasis vulgaris

Reactive neutrophilic

See also: Category:Reactive neutrophilic cutaneous conditions

Reactive neutrophilic cutaneous conditions constitute a spectrum of disease mediated by neutrophils, and typically associated with underlying diseases, such as inflammatory bowel disease and hematologic malignancy.[100][101]

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Pyoderma gangrenosum

Recalcitrant palmoplantar eruptions

See also: Category:Recalcitrant palmoplantar eruptions

Recalcitrant palmoplantar eruptions are skin conditions of the palms and soles which are resistant to treatment.[34]

  • Dermatitis repens (acrodermatitis continua, acrodermatitis continua of Hallopeau, acrodermatitis continua suppurativa Hallopeau, acrodermatitis perstans, dermatitis repens Crocker, Hallopeau's acrodermatitis, Hallopeau's acrodermatitis continua, pustular acrodermatitis)
  • Infantile acropustulosis (acropustulosis of infancy)
  • Palmoplantar pustulosis (persistent palmoplantar pustulosis, pustular psoriasis of the Barber type, pustular psoriasis of the extremities, pustulosis of palms and soles, pustulosis palmaris et plantaris)
  • Pustular bacterid

Resulting from errors in metabolism

See also: Category:Skin conditions resulting from errors in metabolism

Skin conditions resulting from errors in metabolism are caused by enzymatic defects that lead to an accumulation or deficiency of various cellular components, including, but not limited to, amino acids, carbohydrates, and lipids.[16]

Resulting from physical factors

See also: Category:Skin conditions resulting from physical factors

Skin conditions resulting from physical factors occur from a number of causes, including, but not limited to, hot and cold temperatures, friction, and moisture.[34][102][103]

Ionizing radiation-induced

See also: Category:Ionizing radiation-induced cutaneous conditions

Ionizing radiation-induced cutaneous conditions result from exposure to ionizing radiation.[104]

Urticaria and angioedema

See also: Category:Urticaria and angioedema

Urticaria is a vascular reaction of the skin characterized by the appearance of wheals, which are firm, elevated swellings of the skin.[105] Angioedema, which can occur alone or with urticaria, is characterized by a well-defined, edematous swelling that involves subcutaneous tissues, abdominal organs, or upper airway.[106]

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Acute urticaria

Vascular-related

See also: Category:Vascular-related cutaneous conditions

Vascular-related cutaneous conditions result from dysfunction of the blood or blood vessels in the dermis, or lymphatics in the subcutaneous tissues.[9][107][108]

See also

Footnotes

  1. [N 1]
    Any given cutaneous condition is only included once within this list.
  2. [N 2]
    Parentheticals are used to indicate other names by which a condition is known. If there are multiple alternative names for a condition, they are separated by commas within the parenthetical.
  3. [N 3]
    Citations for any given condition name and/or alternative name(s) may be found within the condition's respective article.
  4. [N 4]
    This list uses American English; therefore, the symbols æ and œ, which are common to British English, are not used, but, rather, simplified to a single e. For example, the spelling of nevus is favored over nævus, edema over œdema, and so forth. For more information, see American and British English differences.
  5. [N 5]
    Non-English names are included within this list when those terms are found in English medical literature. Inclusion of acne excoriée des jeunes filles (French), Frambösie (German), and parangi (Malay) represent examples of this convention.
  6. [N 6]
    Abbreviations for condition names commonly described in medical literature with an acronym or initialism are included within this list.
  7. [N 7]
    Within this list, the term immunoglobulin is abbreviated to Ig when used as a prefix to a specific antibody isotype (i.e. IgA, IgD, IgE, IgG, and IgM).
  8. [N 8]
    Within this list, the terms human immunodeficiency virus and acquired immunodeficiency syndrome are abbreviated to HIV and AIDS, respectively.

References

Further reading

External links

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