While the presence of lesions is the denominator among patients with PNP, the characteristics of the lesions differ. The five clinical presentations of lesions associated with PNP include:

- "Pemphigus-like": Flaccid blister (discrete), crusts over the raw exuding skin lesions

- "Pemphigoid-like": Tense blister(s) on brick red erythema

- "Erythema multiforme-like": Severe polymorphic skin and/or mucous membrane lesions

- "Graft-vs.-host disease-like": Widespread lichenoid eruption with severe mucous membrane involvement

- "Lichen planus-like": Small red flat-topped scaly papules

It is most common that mucous membrane lesions of the oral cavity are presented first. They can involve the oropharynx, nasopharynx, tongue, and vermilion (red portion) of the lips. They are also known to develop in the conjunctiva of the eye, anogenital (perineum) region, and esophagus. Cutaneous lesions tend to follow the onset of mucosal lesions. The blisters often erupt in waves, usually affecting the upper trunk, head, neck, and proximal extremities. Pemphigoid-like lesions are seen more often on the extremities. Lichenoid lesions are more common among children, presenting on the trunk and limbs, ranging from small red scaly papules to extensive violet to brown papules extending to the face and neck. Within the spectrum of lichenoid presentations are wounds that have features of erythema multiforme and graft-vs.-host disease. Scaly lesions on the palms of the hand and soles of the feet have been noted to coincide with the lichenoid lesions. Lesions of varying morphology may present simultaneously and transform from one type to another as the disease progresses.

PVA can be characterized by speckled, combined hyper- and hypopigmentation in the plaques or patches of affected skin. Hyperpigmentation is excess coloration, or darkening of the skin, while hypopigmentation is a diminished or pallid coloring to the skin. Pigmentation changes in PVA, apparent in the epidermal (outermost) skin layer, may be attributed to incontinence (leaking out) of melanin from melanocytes into the dermal skin layer below. Inflammation of the skin and cutaneous tissue, common with PVA, also contributes to color changes in the skin, typified by redness. Telangiectasia, the visible "vascular" element of PVA, is the of small blood vessels near the skin surface. Skin atrophy, a wasting-away of the tissue comprising the skin, is a prominent part of PVA and effects the dermal, and particularly the epidermal layer. This, in part, is the result of degenerative of the stratum basale (bottom cell-layer) of the epidermis. Atrophy of the skin gives it a thin, dry and wrinkled appearance, which in PVA-affected individuals has been described as "cigarette paper". Hyperkeratosis, a thickening of the stratum corneum (top cell-layer of the epidermis), has also been reported.

Poikiloderma vasculare atrophicans, or PVA, indicates that extra or altered skin pigmentation ("poikiloderma") is occurring, associated with heightened visibity of capillaries ("", referring to telangiectasia) under the skin, related to thinning and wasting away ("") of the skin and its tissue. Telangiectasia is an enlargement of capillaries underneath the skin.

PVA also has common names that include parapsoriasis-related terminology (i.e. parapsoriasis variagata, or "" parapsoriasis). Parapsoriasis is a term first used by Brocq in 1902, intended to represent a group comprising a number of uncommon skin disorders, under a once used, now antiquated classification scheme for all inflammatory dermatoses (skin diseases known to be associated with or cause inflammation). Brocq chose the term "parapsoriasis" to illustrate that the dermatoses placed in this group had or would have commonalities with psoriasiasis, including appearance and chronicity (lifelong or indefinite duration). This poorly designated grouping has led to confusion in establishing a nosology (a method of classifying diseases and disorders) that associated or distinguished these disorders, and through the years differing opinions and uses regarding parapsoriasis by both authors and physicians has caused further confusion. In more recent times, after much discussion and growing consensus, parapsoriasis and its terminology has been revisited and re-examined often. Newer thought on parapsoriasis, such as by Sutton (1956) all the way to that by Sehgal, "et al." (2007) has cleared much of the confusion and has sparked increased understanding of parapsoriasis and its constituents.

PVA fits within this updated view of parapsoriasis as a syndrome often associated with large plaque parapsoriasis and, or including its variant form, retiform parapsoriasis. Additionally, it may be considered a precursor or variant of the lymphomatous skin disorder mycosis fungoides, which is also associated with large plaque parapsoriasis. Large plaque parapsoriasis consists of inflamed, oddly discolored (such as yellow or blue), web-patterned and scaling plaques on the skin, or larger in diameter. When the condition of the skin encompassed by these plaques worsens and becomes atrophic, it is typically considered retiform parapsoriasis. PVA can occur in either the large plaque or retiform stage, but it can only be considered PVA when its three constituents (poikiloderma, telangiectasia, atrophy) are present. PVA is therefore considered an independent syndrome identified by its constituents, wherever it occurs.

In modern consideration and usage, the solitary term "poikiloderma" has also come to represent all three elements of PVA. When skin diseases and disorders or skin conditions described as dermatoses contain the term poikiloderma in their assessment or diagnosis (such as with Bloom syndrome), this can sometimes be an erroneous usage of the term. Discretion has been advised. Usage of the entire term "poikiloderma vasculare atrophicans" may also be reserved to indicate it as the primary condition affecting the skin in cases where the disorder associated with it is secondary.

Paraneoplastic pemphigus is an autoimmune disorder stemming from an underlying tumor. It is hypothesized that antigens associated with the tumor trigger an immune response resulting in blistering of the skin and mucous membranes.

While patients with malignant and benign tumors are both at risk, malignancy is associated with high mortality rates (near 90%). Current treatment focuses on general wound healing and administering corticosteroids, which has not demonstrated a high success rate. Recent research developments aim to treat the underlying tumor in order to alleviate the symptoms of PNP.

Initial skin findings include red-purple, dusky, flat spots known as macules that start on the trunk and spread out from there. These skin lesions then transform into large blisters. The affected skin can then become necrotic or sag from the body and peel off in great swaths.

There are several types of pemphigus which vary in severity: pemphigus vulgaris, pemphigus foliaceus, Intraepidermal neutrophilic IgA dermatosis, and paraneoplastic pemphigus.

- Pemphigus vulgaris (PV - ICD-10 L10.0) is the most common form of the disorder and occurs when antibodies attack "Desmoglein 3". Sores often originate in the mouth, making eating difficult and uncomfortable. Although pemphigus vulgaris may occur at any age, it is most common among people between the ages of 40 and 60. It is more frequent among Ashkenazi Jews. Rarely, it is associated with myasthenia gravis. Nail disease may be the only finding and has prognostic value in management.

- Pemphigus foliaceus (PF) is the least severe of the three varieties. "Desmoglein 1", the protein that is destroyed by the autoantibody, is found in only the top dry layer of the skin. PF is characterized by crusty sores that often begin on the scalp, and may move to the chest, back, and face. Mouth sores do not occur. This form is also frequent among Ashkenazi Jews. It is not as painful as pemphigus vulgaris, and is often mis-diagnosed as dermatitis or eczema

- Intraepidermal neutrophilic IgA dermatosis is characterized histologically by intraepidermal bullae with neutrophils, some eosinophils, and acantholysis.

- The least common and most severe type of pemphigus is paraneoplastic pemphigus (PNP). This disorder is a complication of cancer, usually lymphoma and Castleman's disease. It may precede the diagnosis of the tumor. Painful sores appear on the mouth, lips, and the esophagus. In this variety of pemphigus, the disease process often involves the lungs, causing bronchiolitis obliterans (constrictive bronchiolitis). Though much less frequent, it is still found the most in the Ashkenazi Jewish population. Complete removal of and/or cure of the tumor may improve the skin disease, but lung damage is generally irreversible.

- Endemic pemphigus foliaceus, including the Fogo Selvagem, the new variant of endemic pemphigus folaiceus in El Bagre, Colombia, South America, and the Tunisian endemic pemphigus in North Africa.

Note that Hailey-Hailey disease, also called familial benign pemphigus, is an inherited (genetic) skin disease, not an autoimmune disease. It is therefore not considered part of the Pemphigus group of diseases.

Nearly all people with TEN have oral, eye and genital involvement as well. Painful crusts and erosions may develop on any mucosal surface. The mouth becomes blistered and eroded, making eating difficult and sometimes necessitating feeding through a nasogastric tube through the nose or a gastric tube directly into the stomach. The eyes can become swollen, crusted, and ulcerated, leading to potential blindness. The most common problem with the eyes is severe conjunctivitis.

NME features a characteristic skin eruption of red patches with irregular borders, intact and ruptured vesicles, and crust formation. It commonly affects the limbs and skin surrounding the lips, although less commonly the abdomen, perineum, thighs, buttocks, and groin may be affected. Frequently these areas may be left dry or fissured as a result. All stages of lesion development may be observed synchronously. The initial eruption may be exacerbated by pressure or trauma to the affected areas.

The histopathologic features of NME are nonspecific and include:

- epidermal necrosis

- subcorneal pustules

- confluent parakeratosis, epidermal hyperplasia, and marked papillary dermal hyperplasia in a psoriasiform pattern

- angioplasia of papillary dermis

- suppurative folliculitis

The vacuolated, pale, swollen epidermal cells and necrosis of the superficial epidermis are most characteristic. Immunofluorescence is usually negative.

Clear cell acanthoma (also known as "Acanthome cellules claires of Degos and Civatte," "Degos acanthoma," and "Pale cell acanthoma") is a benign clinical and histological lesion initially described as neoplastic, which some authors now regard as a reactive dermatosis. It usually presents as a moist solitary firm, brown-red, well-circumscribed, 5 mm to 2 cm nodule or plaque on the lower extremities of middle-aged to elderly individuals The lesion has a crusted, scaly peripheral collarette and vascular puncta on the surface. It is characterized by slow growth, and may persist for years. The clinical differential diagnosis includes: dermatofibroma, inflamed seborrheic keratosis, pyogenic granuloma, basal cell carcinoma, squamous cell carcinoma, verruca vulgaris, psoriatic plaque, and melanoma.

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.

Clear cell acanthoma is characterized by a sharply demarcated psoriasiform epidermal hyperplasia composed of a proliferation of slightly enlarged keratinocytes, and basal cells with pale-staining glycogen-rich cytoplasm, mild spongiosis and scattered neutrophils, which may form small intraepidermal microabscesses. Oedematous dermal papillae are typically seen with increased vascularity and a mixed inflammatory infiltrate including lymphocytes, plasma cells and neutrophils.

Pemphigus ( or ) is a rare group of blistering autoimmune diseases that affect the skin and mucous membranes. The name is derived from the Greek root "pemphix" meaning "pustule".

In pemphigus, autoantibodies form against desmoglein. Desmoglein forms the "glue" that attaches adjacent epidermal cells via attachment points called desmosomes. When autoantibodies attack desmogleins, the cells become separated from each other and the epidermis becomes "unglued", a phenomenon called acantholysis. This causes blisters that slough off and turn into sores. In some cases, these blisters can cover a significant area of the skin.

Originally, the cause of this disease was unknown, and "pemphigus" was used to refer to any blistering disease of the skin and mucosa. In 1964, researchers found that the blood of patients with pemphigus contained antibodies to the layers of skin that separate to form the blisters. In 1971, an article investigating the autoimmune nature of this disease was published.

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.

Intrauterine epidermal necrosis is a cutaneous condition that is rapidly fatal, characterized by skin erosions and ulcerations only.

Erythema multiforme major (also known as "erythema multiforme majus") is a form of rash with skin loss or epidermal detachment.

The term "erythema multiforme majus" is sometimes used to imply a bullous (blistering) presentation.

According to some sources, there are two conditions included on a spectrum of this same disease process:

- Stevens–Johnson syndrome (SJS)

- Toxic epidermal necrolysis (TEN) which described by Alan Lyell and previously called Lyell syndrome[5].

In this view, EM major, SJS and TEN are considered a single condition, distinguished by degree of epidermal detachment.

However, a consensus classification separates erythema multiforme minor, erythema multiforme major, and SJS/TEN as three separate entities.

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.

A seborrheic keratosis, also known as seborrheic verruca, basal cell papilloma, or a senile wart, is a non-cancerous (benign) skin tumour that originates from cells in the outer layer of the skin (keratinocytes). Like liver spots, seborrheic keratoses are seen more often as people age.

The tumours (also called lesions) appear in various colours, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than across. They can often come in association with other skin conditions, including basal cell carcinoma. Sometimes seborrheic keratosis and basal cell carcinoma occur at the same location, and sometimes seborrheic keratosis progresses to basal cell carcinoma. At clinical examination the differential diagnosis include warts and melanoma. Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts", because they resemble warts, but strictly speaking the term "warts" refers to lesions that are caused by human papillomavirus.

The condition varies from a mild, self-limited rash (E. multiforme minor) to a severe, life-threatening form known as erythema multiformer major (or erythema multiforme majus) that also involves mucous membranes.

Consensus classification:

- Erythema multiforme minor—typical targets or raised, edematous papules distributed

- Erythema multiforme major—typical targets or raised, edematous papules distributed acrally with involvement of one or more mucous membranes; epidermal detachment involves less than 10% of total body surface area (TBSiA)

- SJS/TEN—widespread blisters predominant on the trunk and face, presenting with erythematous or pruritic macules and one or more mucous membrane erosions; epidermal detachment is less than 10% TBSA for Stevens-Johnson syndrome and 30% or more for toxic epidermal necrolysis.

The mild form usually presents with mildly itchy (but itching can be very severe), pink-red blotches, symmetrically arranged and starting on the extremities. It often takes on the classical "target lesion" appearance, with a pink-red ring around a pale center. Resolution within 7–10 days is the norm.

Individuals with persistent (chronic) erythema multiforme will often have a lesion form at an injury site, e.g. a minor scratch or abrasion, within a week. Irritation or even pressure from clothing will cause the erythema sore to continue to expand along its margins for weeks or months, long after the original sore at the center heals.

Epidermolytic hyperkeratosis is a skin disorder that is present at birth. Affected babies may have very red skin (erythroderma) and severe blisters. Because newborns with this disorder are missing the protection provided by normal skin, they are at risk of becoming dehydrated and developing infections in the skin or throughout the body (sepsis).

As affected individuals get older, blistering is less frequent, erythroderma becomes less evident, and the skin becomes thick (hyperkeratotic), especially over joints, on areas of skin that come into contact with each other, or on the scalp or neck. This thickened skin is usually darker than normal. Bacteria can grow in the thick skin, often causing a distinct odor.

Epidermolytic hyperkeratosis can be categorized into two types. People with PS-type epidermolytic hyperkeratosis have thick skin on the palms of their hands and soles of their feet (palmoplantar or palm/sole hyperkeratosis) in addition to other areas of the body. People with the other type, NPS-type, do not have extensive palmoplantar hyperkeratosis but do have hyperkeratosis on other areas of the body.

Epidermolytic hyperkeratosis is part of a group of conditions called ichthyoses, which refers to the scaly skin seen in individuals with related disorders. However, in epidermolytic hyperkeratosis, the skin is thick but not scaly as in some of the other conditions in the group.

"http://ghr.nlm.nih.gov/condition/epidermolytic-hyperkeratosis"

Pemphigus herpetiformis (also known as "Acantholytic herpetiform dermatitis," "Herpetiform pemphigus," "Mixed bullous disease," and "Pemphigus controlled by sulfapyridine") is a cutaneous condition, a clinical variant of pemphigus that combines the clinical features of dermatitis herpetiformis with the immunopathologic features of pemphigus.

Pathophysiology:

Pemphigus Herpetiformis is an IGg mediated autoantibodies that affect the epidermal layer of the skin.

The disease presents with the widespread formation of fluid-filled blisters that are thin walled and easily ruptured and the patient can be positive for Nikolsky's sign. Ritter's Disease of the Newborn is the most severe form of SSSS with similar signs and symptoms. SSSS often includes a widespread painful erythroderma, often involving the face, diaper, and other intertriginous areas. Extensive areas of desquamation might be present. Perioral crusting and fissuring are seen early in the course. Unlike toxic epidermal necrolysis, SSSS spares the mucous membranes. It is most common in children under 6 years, but can be seen in adults who are immunosuppressed or have renal failure.

Florid cutaneous papillomatosis (also known as the Schwartz-Burgess syndrome) is an obligate paraneoplastic syndrome.

FCP begins as the sudden onset of numerous cutaneous papillomas that are clinically indistinguishable from viral warts. The papillomas range from 1 to 3 mm in diameter may spread to involve the entire body, including the face. Pruritus, which may sometimes precede the onset of FCP, is evident in the affected regions in about half of patients. Evaluation of a skin biopsy clearly distinguishes FCP from viral warts.

FCP is associated with underlying cancer of the breast, bladder, ovary, uterus, prostate, and lung. Other associated underlying malignancies include squamous cell carcinomas and lymphomas such as non-Hodgkin's lymphoma.

FCP is sometimes seen together with other signs of internal cancer, especially malignant acanthosis nigricans, tripe palms, Leser–Trélat sign, and hypertrichosis lanuginosa acquisita. FCP tends to improve in association with surgical or chemotherapeutic therapy of the underlying internal cancer. A recurrence or exacerbation of FCP may be linked with tumor regrowth or metastatic spread.

Hypermelanotic nevi must be differentiated from other types of pigmented skin lesions, including:

- Lentigo simplex

- Solar lentigo

- Café au lait macule

- Ink-spot lentigo

- Mucosal melanotic macule

- Mongolian spot (dermal melanocytosis)

The characteristic eruption is of multiple warty papules and nodules beginning on acral skin, especially the hands and wrists, and disseminating onto the skin of the entire body. These skin lesions develop on the trunk, extremities, and face, and are almost twice as common in men than in women, especially individuals aged 53–72 years. Pruritus is also associated.