As PNP is ultimately caused by the presence of a tumor, it is not contagious. There is no known way to predict who will become afflicted with it. Patients with cancer are therefore a group at risk. Although PNP has been known to affect all age groups, it is more likely to afflict middle-aged to older patients.

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 People with SJS or TEN caused by a medications have a better prognosis the earlier the causative medication is withdrawn.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.

Urbach–Wiethe disease is very rare; there are fewer than 300 reported cases in medical literature. Although Urbach–Wiethe disease can be found worldwide, almost a quarter of reported diagnoses are in South Africa. Many of these are in patients of Dutch, German, and Khoisan ancestry. This high frequency is thought to be due to the founder effect. Due to its recessive genetic cause and the ability to be a carrier of the disease without symptoms, Urbach–Wiethe disease often runs in families. In some regions of South Africa, up to one in 12 individuals may be carriers of the disease. Most of the case studies involving Urbach–Wiethe disease patients involve only one to three cases and these cases are often in the same family. Due to its low incidence, it is difficult to find a large enough number of cases to adequately study the disease.

Inflammatory Linear Verrucous Epidermal Nevus (ILVEN) is a rare disease of the skin that presents as multiple, discrete, red papules that tend to coalesce into linear plaques that follow the Lines of Blaschko. The plaques can be slightly warty (psoriaform) or scaly (eczema-like). ILVEN is caused by somatic mutations that result in genetic mosaicism. There is no cure, but different medical treatments can alleviate the symptoms.

Epidermolysis bullosa dystrophica or dystrophic EB (DEB) is an inherited disease affecting the skin and other organs.

"Butterfly child" is the colloquial name for a child born with the disease, as their skin is seen to be as delicate and fragile as that of a butterfly.

If the lesions are mild, the patient will be subject to a good deal of pain. If the lesions are severe, the overall quality of life is devastating. The impaired skin barrier function commonly leads to localized infection, which sepsis and death may follow. The pain from the oral and pharyngeal ulcers interfere with eating, which can compromise nutritional health.

The general prognosis for PNP is poor. It is more hopeful if the tumor is benign, but in the case of malignant tumors, the mortality rate is roughly 90%. The two most commonly associated types of tumors are non-Hodgkin lymphoma and chronic lymphocytic lymphoma; nearly all of these patients die within two years of diagnosis. This is attributed to the effects of the tumor combined with the negative side effects of the medication administered to treat PNP.

Roughly 1/3 of the deaths from PNP stem from pulmonary insufficiency which is brought about by the action of PNP on the respiratory mucosa. It manifests as dyspnea and progresses to bronchiolitis obliterans (non-reversible obstructive lung disease) via an unknown mechanism.

Most cases are sporadic, but a familial case, with the condition occurring in a mother and her daughter, has been described.

It also has been proposed that activation of an autosomal dominant lethal mutation that survives by mosaicism may be the cause of the lesions. The mutated cells may survive in the due to proximity of normal cells. Another theory is that retrotransposable elements may be the cause of all skin conditions along the Lines of Blashko. Some dogs have a coat variation based upon a similar mechanism.

The classification of the disease has much to do with the appearance and location of the lesions (phenotype characteristics). As this is a rare condition, it is possible that more than one genotype could cause a similar phenotype. Different genes have been implicated, but the number of patients studied in each case is very low.

There is some evidence that interleukins 1 and 6, tumor necrosis factor α, and intercellular adhesion molecule-1 are upregulated in ILVEN, similar to psoriasis.

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.

An extremely rare disease of which only a few isolated cases are known.

Urbach–Wiethe disease is typically not a life-threatening condition. The life expectancy of these patients is normal as long as the potential side effects of thickening mucosa, such as respiratory obstruction, are properly addressed. Although this may require a tracheostomy or carbon dioxide laser surgery, such steps can help ensure that individuals with Urbach–Wiethe disease are able to live a full life. Oral dimethyl sulfoxide (DMSO) has been shown to reduce skin lesions, helping to minimize discomfort for these individuals.

PVA usually has an underlying cause, attributed to existing skin diseases and disorders associated with a cutaneous lymphoma or inflammation. Mycosis fungoides is the common lymphoma believed to cause PVA, although it may be considered a precursor when the lymphoma is (hidden) and undiagnosed. Large plaque parapsoriasis is another common causes of PVA. Less common causes include autoimmune-related connective tissue diseases such as lupus, dermatomyositis and scleroderma. Dermatoses and those that are genetically inspired, called genodermatoses, may also be an underlying cause of PVA. Among them, xeroderma pigmentosum and Rothmund-Thomson syndrome (poikiloderma congenita) are thought to be the most prominent. Ingestion of substances containing arsenic, such as arsphenamine, has also been suggested as a least common cause. PVA can also be idiopathic (of unknown cause), as seen in a small number of cases.

Howel–Evans syndrome is an extremely rare condition involving thickening of the skin in the palms of the hands and the soles of the feet (hyperkeratosis). This familial disease is associated with a high lifetime risk of esophageal cancer. For this reason, it is sometimes known as tylosis with oesophageal cancer (TOC).

The condition is inherited in an autosomal dominant manner, and it has been linked to a mutation in the "RHBDF2" gene. It was first described in 1958.

RHBDF2 may also play a role in ovarian epithelial cancer.

Possible associations with gastric cancer and lung cancer have been suggested. Other possible associations include corneal defects, congenital pulmonary stenosis, total anomalous pulmonary venous connection deafness and optic atrophy.

One of the biggest risks factors faced by the affected foals is susceptibility to secondary infection. Within three to eight days after birth, the foal may die from infection or is euthanized for welfare reasons.

Ichthyosis hystrix is a group of rare skin disorders in the ichthyosis family of skin disorders characterized by massive hyperkeratosis with an appearance like spiny scales. This term is also used to refer to a type of epidermal nevi with extensive bilateral distribution.

Frequencies of this disease are the greatest in Norway with a few Finnish cases have also having been noted to date. Some cases have been found in other ethnicities such as in people of Indian or Japanese descent as well as a north Italian family. These cases are scattered and there are potentially more under reported cases as this disease is often under diagnosed for other cutaneous diseases. It is most prevalent in a defined region in the middle of Norway and Sweden with a heterozygote carrier frequency of 1 in 50.

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.

The signs of sebaceous adenitis are caused by an inflammatory disease process which affects the sebaceous glands of the skin. The cause of the inflammatory disease is unknown. Different breeds of dogs may have different underlying causes of the disease.

Research is currently underway to find if there is a genetic predisposition for sebaceous adenitis; the exact mode of inheritance remains unknown.

In Standard Poodles, sebaceous adenitis is most likely an autosomal recessive inherited disease, with variable expression.

The deficiency in anchoring fibrils impairs the adherence between the epidermis and the underlying dermis. The skin of DEB patients is thus highly susceptible to severe blistering.Collagen VII is also associated with the epithelium of the esophageal lining, and DEB patients may suffer from chronic scarring, webbing, and obstruction of the esophagus. Affected individuals are often severely malnourished due to trauma to the oral and esophageal mucosa and require feeding tubes for nutrition. They also suffer from iron-deficiency anemia of uncertain origin, which leads to chronic fatigue.

Open wounds on the skin heal slowly or not at all, often scarring extensively, and are particularly susceptible to infection. Many individuals bathe in a bleach and water mixture to fight off these infectionsThe chronic inflammation leads to errors in the DNA of the affected skin cells, which in turn causes squamous cell carcinoma (SCC). The majority of these patients die before the age of 30, either of SCC or complications related to DEB.

The chronic inflammatory state seen in recessive dystrophic epidermolysis bullosa (RDEB) may cause Small fiber peripheral neuropathy (SFN).; RDEB patients have reported the sensation of pain in line with neuropathic pain qualities.

In general, sebaceous adenitis is underdiagnosed in dogs. Diagnosis confirmation requires multiple punch biopsies analysed by a dermopathologist who will comment on the condition of the sebaceous glands, revealing granulomatous or pyogranulomatous inflammation surrounding the sebaceous glands or even complete destruction of sebaceous glands.

Other conditions with similar presentations include: bacterial folliculitis and demodicosis, dermatophytosis, endocrinopathy, pemphigus foliaceus, zinc responsive dermatosis, vitamin A-responsive dermatosis, ichthyosis, and nutritional deficiencies. As well as, superficial pyoderma, primary idiopathic seborrhea and other endocrine diseases.

The decision to observe or treat a nevus may depend on a number of factors, including cosmetic concerns, irritative symptoms (e.g., pruritus), ulceration, infection, and concern for potential malignancy.

William Becker first described an association between NME and glucagonoma in 1942 and since then, NME has been described in as many as 70% of individuals with a glucagonoma. NME is considered part of the glucagonoma syndrome, which is associated with hyperglucagonemia, diabetes mellitus, and hypoaminoacidemia.

When NME is identified in the absence of a glucagonoma, it may be considered "pseudoglucagonoma syndrome". Less common than NME with glucagonoma, pseudoglucagonoma syndrome may occur in a number of systemic disorders:

- Celiac disease

- Ulcerative colitis

- Crohn's disease

- Hepatic cirrhosis

- Hepatocellular carcinoma

- Lung cancer, including small cell lung cancer

- Tumors that secrete insulin- or insulin-like growth factor 2

- Duodenal cancer

Currently, there are no treatments available for JEB. However, the disorder can be prevented through good breeding management. Horses that are carriers of JEB should not be incorporated into breeding programs. Although, if breeders are insistent on breeding a carrier, precautions need to be taken to ensure that the other mate is not a carrier as well. Genetic testing for the disorder is highly recommended among breeding programs for the Draft horse and Saddlebred breeds to determine their carrier status.

Eosinophils are a kind of a white blood cell which help protect the body from certain infections and involved in allergic responses. Eosionphelia is an abnormal increase of eosinophils in tissue, blood or both and is present in individuals born with this syndrome.

Epidermolytic ichthyosis (EI), (also known as "epidermolytic hyperkeratosis (EHK)", "bullous congenital ichthyosiform erythroderma (BCIE), bullous ichthyosiform erythroderma, or bullous congenital ichthyosiform erythroderma Brocq) is a rare and severe form of ichthyosis this skin disease affects around 1 in 300,000 people.

It involves the clumping of keratin filaments.