The mortality for toxic epidermal necrolysis is 25-30%. People with SJS or TEN caused by a medications have a better prognosis the earlier the causative medication is withdrawn. Loss of the skin leaves patients vulnerable to infections from fungi and bacteria, and can result in sepsis, the leading cause of death in the disease. Death is caused either by infection or by respiratory distress which is either due to pneumonia or damage to the linings of the airway. Microscopic analysis of tissue (especially the degree of dermal mononuclear inflammation and the degree of inflammation in general) can play a role in determining the prognosis of individual cases.

Many 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. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square meters, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. 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. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. 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.

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. 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. 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. 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.

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. 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. 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.

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. 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. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.

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). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. 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. 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). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

"Junctional epidermolysis bullosa with pyloric atresia" is a rare autosomal recessive form of junctional epidermolysis bullosa that presents at birth with severe mucocutaneous fragility and gastric outlet obstruction. It can be associated with "ITGB4" or "ITGA6".

Peeling skin syndrome (also known as "Acral peeling skin syndrome," "Continual peeling skin syndrome," "Familial continual skin peeling," "Idiopathic deciduous skin," and "Keratolysis exfoliativa congenita") is an autosomal recessive disorder characterized by lifelong peeling of the stratum corneum, and may be associated with pruritus, short stature, and easily removed anagen hair.

The acral form can be associated with "TGM5".

"Junctional epidermolysis bullosa gravis" (also known as "Herlitz disease," "Herlitz syndrome," and "Lethal junctional epidermolysis bullosa") is the most lethal type of epidermolysis bullosa, a skin condition in which most patients do not survive infancy, characterized by blistering at birth with severe and clinically distinctive perorificial granulation tissue.

JEB-H is generally caused by mutations in one of the three laminin-332 coding genes: LAMA3 (18q11.2), LAMB3 (1q32) and LAMC2 (1q25-q31).

Although there are likely to be multiple genetic factors and environmental triggers, mutations causing defects in the IL-36RN, CARD14 and AP1S3 genes have been shown to cause GPP .

The term pustular psoriasis is used for a heterogeneous group of diseases that share pustular skin characteristics.

Most cases of generalized pustular psoriasis present in patients with existing or prior psoriasis conditions. However, there are many cases of GPP that arise without a history of psoriasis.

The Department of Dermatology of the University of São Paulo proposed a classification for these two conditions. Pso+ represents patients with a personal history of psoriasis and pso- represents patients with no history of psoriasis. They also identified a common factor among patients in each group: In the pso+ group, the most common precipitating factor is corticosteroid withdrawal. In the pso- group, the most common precipitating factor is infection.

In a large portion of cases, the disease is brought on by some triggering factor. Through research and observation, many of these factors have been identified. The following table, from an article in Cutis, lists a few factors that have been observed as influential in the onset of GPP.

Source: “Table II”, “Pustular Psoriasis” Farber and Nall, 1993

A survey of 10,000 American households revealed that the prevalence of diagnosed primary immunodeficiency approaches 1 in 1200. This figure does not take into account people with mild immune system defects who have not received a formal diagnosis.

Milder forms of primary immunodeficiency, such as selective immunoglobulin A deficiency, are fairly common, with random groups of people (such as otherwise healthy blood donors) having a rate of 1:600. Other disorders are distinctly more uncommon, with incidences between 1:100,000 and 1:2,000,000 being reported.

Diseases of the skin include skin infections and skin neoplasms (including skin cancer).

Generalized granuloma annulare is a skin condition of unknown cause, tending to affect women in the fifth and sixth decades, presenting as a diffuse but symmetrical, papular or annular eruption of more than ten skin lesions, and often hundreds.

HIV-positive individuals have 1000 times the risk of developing SJS/TEN compared to the general population. The reason for this increased risk is not clear.

Granuloma annulare in HIV disease is a skin condition characterized typically by papular and generalized skin lesions.

It is estimated that 2—3 percent of hospitalised patients are affected by a drug eruption, and that serious drug eruptions occur in around 1 in 1000 patients.

Porokeratosis is a specific disorder of keratinization that is characterized histologically by the presence of a cornoid lamella, a thin column of closely stacked, parakeratotic cells extending through the stratum corneum with a thin or absent granular layer.

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

- Acute radiodermatitis

- Chronic radiation keratosis

- Chronic radiodermatitis

- Eosinophilic, polymorphic, and pruritic eruption associated with radiotherapy

- Fluoroscopy burn

- Radiation acne

- Radiation cancer

- Radiation dermatitis (radiodermatitis)

- Radiation recall reaction

- Radiation-induced erythema multiforme

- Radiation-induced hypertrophic scar

- Radiation-induced keloid

- Radiation-induced morphea

Lymphomatoid papulosis (LyP) is a rare skin disorder. The overall prevalence rate of lymphomatoid papulosis is estimated at 1.2 to 1.9 cases per 1,000,000 population.This rare condition has only been studied in depth since 1968.

By definition, primary immune deficiencies are due to genetic causes. They may result from a single genetic defect, but most are multifactorial. They may be caused by recessive or dominant inheritance. Some are latent, and require a certain environmental trigger to become manifest, like the presence in the environment of a reactive allergen. Other problems become apparent due to aging of bodily and cellular maintenance processes.

A cutaneous condition is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment.

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). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying causes and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), cause (skin conditions resulting from physical factors), and so on.

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). The diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data. The introduction of cutaneous ultrasound has allowed the detection of cutaneous tumors, inflammatory processes, nail disorders and hair diseases.

Pustular psoriasis is classified into two major forms: localized and generalized pustular psoriasis. Within these two categories there are several variants:

X-linked reticulate pigmentary disorder (also known as "familial cutaneous amyloidosis", "Partington amyloidosis", "Partington cutaneous amyloidosis", "Partington syndrome type II", "reticulate pigmentary disorder", and "X-linked reticulate pigmentary disorder with systemic manifestations") is a cutaneous condition that has been described in adult women that had linear streaks of hyperpigmentation and in which male patients manifested a reticulated mottled brown pigmentation of the skin, which, on biopsy, demonstrated dermal deposits of amyloid.

The syndrome is also referred with the acronym X-Linked-PDR or even XLPRD.It's a very rare disease, genetically determined, with a chronic course.

It was characterized in 1981. Mutation of the "POLA1" gene leads to loss of expression of the catalytic subunit of DNA polymerase-α and is responsible for XLPDR. Loss of POLA1 expression results in reduced levels of RNA:DNA hybrids in the cytosol and unexpectedly triggers aberrant immune responses (e.g. type I interferon production) which at least in part can account for the symptoms associated with XLPDR.

Variations in genes that are part of the immune system or part of melanocytes have both been associated with vitiligo. It is also thought to be caused by the immune system attacking and destroying the melanocytes of the skin. A genomewide association study found approximately 36 independent susceptibility loci for generalized vitiligo.

Although multiple hypotheses have been suggested as potential triggers that cause vitiligo, studies strongly imply that changes in the immune system are responsible for the condition. Vitiligo has been proposed to be a multifactorial disease with genetic susceptibility and environmental factors both thought to play a role.

The TYR gene encodes the protein tyrosinase, which is not a component of the immune system, but is an enzyme of the melanocyte that catalyzes melanin biosynthesis, and a major autoantigen in generalized vitiligo. The NIH states that sunburns can cause the disease but there is not good evidence to support this.

Preliminary evidence suggests a possible association with eating gluten.

In most cases, cutis laxa is inherited. Autosomal dominant, autosomal recessive, and X-linked recessive forms have been described, but acquired forms also occur.

Cutis laxa is associated with deficient or absent elastin fibers in the extracellular matrix. Various mutations in genes have been identified.

Cutis laxa may be caused by mutations in the genes: "ELN", "ATP6V0A2",

ATP7A, "FBLN4", "FBLN5", and "PYCR1". A related neurocutaneous syndrome may be caused by mutations in the gene "ALDH18A1" ("P5CS").

Congenital Ichthyosiform Erythroderma (CIE), also known as Nonbullous congenital ichthyosiform erythroderma is a rare type the ichthyosis family of skin diseases which occurs in 1 in 200,000 to 300,000 births.