IgA pemphigus is a subtype of pemphigus with two distinct forms:

- "Subcorneal pustular dermatosis" (also known as Sneddon–Wilkinson disease and pustulosis subcornealis) is skin condition that is a rare, chronic, recurrent, pustular eruption characterized histopathologically by subcorneal pustules that contain abundant neutrophils. This is distinct from and not to be confused with subcorneal pustular dermatosis type of IgA pemphigus. Sneddon's syndrome, also known as Ehrmann-Sneddon syndrome, is also a different syndrome.

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

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.

The forms of pemphigoid are considered to be connective tissue autoimmune skin diseases. There are several types:

- Gestational pemphigoid or Pemphigoid gestationis (PG) (formerly called Herpes gestationis)

- Bullous pemphigoid (BP) Rarely affect the mouth

- Mucous membrane pemphigoid, also known as Cicatricial pemphigoid (CP) (No skin involvement)

Bullous and Cicatricial pemphigoids usually affect persons who are over age 60. Gestational pemphigoid occurs during pregnancy, typically in the second or third trimester, and/or immediately following pregnancy.

Acrodermatitis /ac·ro·der·ma·ti·tis/ is a childhood form of dermatitis selectively affecting the hands and feet and may be accompanied by mild symptoms of fever and malaise. It may also be associated with hepatitis B and other viral infections.

The lesions appear as small coppery-red, flat-topped firm papules that appear in crops and sometimes in long linear strings, often symmetric.

It is a diffuse chronic skin disease usually confined to the limbs, seen mainly in women in Northern, Central, and Eastern Europe, and characterized initially by an erythematous, oedematous, pruritic phase followed by sclerosis and atrophy. It is caused by infection with "Borrelia burgdorferi".

Clinically, the earliest lesions may appear urticarial (like hives), but could also appear dermatitic, targetoid, lichenoid, nodular, or even without visible rash (essential pruritus). Tense bullae eventually erupt, most commonly at the inner thighs and upper arms, but the trunk and extremities are frequently both involved. Any part of the skin surface can be involved. Oral lesions are present in a minority of cases. The disease may be acute, but typically will wax and wane. Several other skin diseases may have similar symptoms. However, milia are more common with epidermolysis bullosa acquisita, because of the deeper antigenic targets. A more ring-like configuration, with a central depression or centrally collapsed bullae may indicate linear IgA disease. Nikolsky's sign is negative unlike pemphigus vulgaris where it is positive.

A vesiculobullous disease is a type of mucocutaneous disease characterized by vesicles and bullae (i.e. blisters). Both vesicles and bullae are fluid-filled lesions, and they are distinguished by size (vesicles being less than 5–10 mm and bulla being larger than 5–10 mm, depending upon which definition is used). In the case of vesiculobullous diseases which are also immune disorders, the term "immunobullous" is sometimes used. Examples of vesiculobullous diseases include:

- "Infectious: (viral)"

- Herpes simplex

- Varicella-Zoster infection

- Hand, foot and mouth disease

- Herpangina

- Measles (Rubeola)

- "Immunobullous:"

- Pemphigus vulgaris

- Pemphigoid

- Dermatitis herpetiformis

- Linear immunoglobulin-A disease (linear IgA disease)

- "Genetic:"

- Epidermolysis bullosa

Some features are as follows:

Initially red to pink, flat spots (formally, "macules") and raised bumps (formally, "papules") may be seen on the skin.

Once fully developed, the classic appearance is "non-blanching, palpable purpura". This appears as deep red to purple spots that feel raised to the touch. Purpura refers to the red-purple discolored spots, while palpable implies that these spots can be felt as raised from the surrounding skin. Additionally, when gently pressed, the color does not fade to a lighter color ("non-blanching"). The red-purple color of the lesions is due to the inflammation in the blood vessels causing red blood cells to escape into the dermis skin layer.

Small fluid-filled blisters (or "vesicles"), pus-filled bumps resembling a pimple (or "pustules"), or shallow ulcers may also develop but are less common.

The location of skin lesions varies but are most commonly found symmetrically below the waist, primarily on the buttocks and legs. Other distributions include localized areas on the upper body or over several areas of the body.

With treatment, the lesions typically resolve in weeks to months and leave behind flat spots that are darker than the surrounding skin. (see "Postinflammatory hyperpigmentation" on "Hyperpigmentation")

A portion of cases may be persistent or recurrent. This tends to occur when the vasculitis is associated with chronic conditions such as connective tissue diseases.

Linear IgA bullous dermatosis is frequently associated with medication exposure, especially vancomycin, with men and women being equally affected. It was first described by Tadeusz Chorzelski in 1979. Linear IgA dermatosis is a rare immune-mediated blistering skin disease that may be divided into two types:

- "Adult linear IgA disease" is an acquired, autoimmune blistering disease that may present with a clinical pattern of vesicles indistinguishable from dermatitis herpetiformis, or with vesicles and bullae in a bullous pemphigoid-like appearance. This disease can often be difficult to treat even with usually effective medications such as rituximab.

- "Childhood linear IgA disease" (also known as "Chronic bullous disease of childhood") is an acquired, self-limited bullous disease that may begin by the time the patient is age 2 to 3 and usually remits by age 13.

Pemphigoid is a group of rare autoimmune blistering skin diseases. As its name indicates, pemphigoid is similar in general appearance to pemphigus, but, unlike pemphigus, pemphigoid does not feature acantholysis, a loss of connections between skin cells.

Pemphigoid is more common than pemphigus, and is slightly more common in women than in men. It is also more common in people over 60 years of age than it is in younger people.

Types include:

- Acrodermatitis enteropathica

- Acropustulosis

- Acrodermatitis chronica atrophicans

- Papular acrodermatitis of childhood

- Dermatitis repens

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.

In most cases skin lesions do not cause symptoms, however itching, burning, or pain may occur.

Frequently reported symptoms include mild fever, muscle pain, joint pain, or an overall feeling of discomfort. Additional symptoms depend on the cause of the vasculitis and if other organ systems are involved. For example, if the vasculitis is a manifestation of Henoch-Schönlein purpura, individuals may also experience abdominal pain or blood in the urine.

Bullous pemphigoid is an acute or chronic autoimmune skin disease, involving the formation of blisters, more appropriately known as bullae, at the space between the epidermis and dermis skin layers. It is classified as a type II hypersensitivity reaction, with the formation of anti-hemidesmosome antibodies.

Chronic and repetitive scratching, picking, or rubbing of the nodules may result in permanent changes to the skin, including nodular lichenification, hyperkeratosis, hyperpigmentation, and skin thickening. Unhealed, excoriated lesions are often scaly, crusted or scabbed. Many patients report a lack of wound healing even when medications relieve the itching and subsequent scratching.

Patients often:

- seek treatment during middle-age, although PN can occur at any age.

- have a history of chronic severe pruritus.

- have a significant medical history for unrelated conditions.

- suffer from liver or kidney dysfunctions.

- suffer secondary skin infections.

- have a personal or family history of atopic dermatitis.

- have other autoimmune disorders.

- have low vitamin D levels.

The cause of prurigo nodularis is unknown, although other conditions may induce PN. PN has been linked to Becker's nevus, linear IgA disease, an autoimmune condition, liver disease and T cells. Systemic pruritus has been linked to cholestasis, thyroid disease, polycythaemia rubra vera, uraemia, Hodgkins disease, HIV and other immunodeficiency diseases. Internal malignancies, liver failure, renal failure, and psychiatric illnesses have been considered to induce PN, although more recent research has refuted a psychiatric cause for PN. Patients report an ongoing battle to distinguish themselves from those with psychiatric disorders such as delusions of parasitosis and other psychiatric conditions.

ILVEN is a condition that normally only affects one side of the body (unilateral). Usually the left side of patients is affected. The condition is persistent and forms along characteristic lines. It usually appears on an extremity in infancy or childhood. Altman and Mehregan described six characteristic features of ILVEN: (1) early age of onset, (2) predominance in females (4:1 female-male ratio), (3) frequent involvement of the left leg, (4) pruritus, or "itchiness" (5) marked refractoriness to therapy, and (6) a distinctive psoriasiform and inflammatory histologic appearance.

In humans, eosinophilic granulomas are considered a benign histiocytosis that occurs mainly in adolescents and young adults. Clinically, unifocal lytic lesions are found in bones such as the skull, ribs and femur. Because of this, bone pain and pathologic fractures are common.

Aside from the mosquito allergy cat, cats with EGC usually have allergy, ectoparasite infestation or possibly ringworm or other skin infection. Other implicated causes include traumatic damage, autoimmune disease or FeLV infection.

Early descriptions were made by Darrell Wilkinson, a British dermatologist.

Dermatitis herpetiformis is characterized by intensely itchy, chronic papulovesicular eruptions, usually distributed symmetrically on extensor surfaces (buttocks, back of neck, scalp, elbows, knees, back, hairline, groin, or face). The blisters vary in size from very small up to 1 cm across.

The condition is extremely itchy, and the desire to scratch can be overwhelming. This sometimes causes the sufferer to scratch the blisters off before they are examined by a physician. Intense itching or burning sensations are sometimes felt before the blisters appear in a particular area.

Untreated, the severity of DH can vary significantly over time, in response to the amount of gluten ingested.

Dermatitis herpetiformis symptoms typically first appear in the early years of adulthood between 20 and 30 years of age.

Although the first signs and symptoms of dermatitis herpetiformis are intense itching and burning, the first visible signs are the small papules or vesicles that usually look like red bumps or blisters. The rash rarely occurs on other mucous membranes, excepting the mouth or lips. The symptoms range in severity from mild to serious, but they are likely to disappear if gluten ingestion is avoided and appropriate treatment is administered.

Dermatitis herpetiformis symptoms are chronic, and they tend to come and go, mostly in short periods of time. Sometimes, these symptoms may be accompanied by symptoms of coeliac disease, commonly including abdominal pain, bloating or loose stool, and fatigue.

The rash caused by dermatitis herpetiformis forms and disappears in three stages. In the first stage, the patient may notice a slight discoloration of the skin at the site where the lesions appear. In the next stage, the skin lesions transform into obvious vesicles and papules that are likely to occur in groups. Healing of the lesions is the last stage of the development of the symptoms, usually characterized by a change in the skin color. This can result in areas of the skin turning darker or lighter than the color of the skin on the rest of the body. Because of the intense itching, patients usually scratch, which can lead to the formation of crusts.

85–90% of IgA-deficient individuals are asymptomatic, although the reason for lack of symptoms is relatively unknown and continues to be a topic of interest and controversy. Some patients with IgA deficiency have a tendency to develop recurrent sinopulmonary infections, gastrointestinal infections and disorders, allergies, autoimmune conditions, and malignancies. These infections are generally mild and would not usually lead to an in-depth workup except when unusually frequent.

They may present with severe reactions including anaphylaxis to blood transfusions or intravenous immunoglobulin due to the presence of IgA in these blood products. Patients have an increased susceptibility to pneumonia and recurrent episodes of other respiratory infections and a higher risk of developing autoimmune diseases in middle age.

IgA deficiency and common variable immunodeficiency (CVID) feature similar B cell differentiation arrests, it does not present the same lymphocyte subpopulation abnormalities. IgA-deficient patients may progress to panhypogammaglobulinemia characteristic of CVID. Selective IgA and CVID are found in the same family.

Affected males develop generalized reticular hyper pigmentation in early childhood.

Hair often looks bedraggled or brushed backwards, hanging low on the forehead.

Among the associated extracutaneous manifestations are described:

- Respiratory infections

- Dyskeratosis corneal photophobia

- Hypohidrosis with large deficit of thermoregulation

- Growth retardation

- Gastrointestinal disorders

- Kidney disease

- Kidney stones

- Urinary infections

- Webbed feet or hands

- Electrolyte imbalance

- Retinitis pigmentosa

- Lymphoedema

- Thyroid abnormalities

Each patient shows some of the symptoms listed above. Not every sick person will show all of the listed symptoms.

In females the disease is characterized by skin rashes linear hyper pigmentation following the Blaschko's lines, morphologically similar to stage 3 pigment incontinence. There are no systemic manifestations associated with XLPDR in females.

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.

Hypersensitivity vasculitis (allergic vasculitis). Usually due to a hypersensitivity reaction to a known drug. Drugs most commonly implicated are penicillin, sulphonamides and thiazide diuretics. There is presence of skin vaculitis with palpable petechiae or purpura. Biopsy of these lesions reveal inflammation of the small vessels, termed leukocytoclastic vasculitis, which is most prominent in postcapillary venules. At least 3 out of 5 criteria yields sensitivity and specificity of 71 and 84%:

- age > 16

- use of possible triggering drug in relation to symptoms

- palpable purpura

- maculopapular rash

- skin biopsy showing neutrophils around vessel

IgA vasculitis (IgAV; formerly known as Henoch-Schonlein purpura). Systemic vasculitis due to tissue deposition of IgA-containing immune complexes. Biopsy of lesions shows inflammation of small vessels. It is considered a form of hypersensitivity vasculitis but is distinguished by prominent deposits of IgA. This is the most common vasculitis in children. Presence of 3 or more criteria yielded sensitivity of 87% while less than 2 criteria yielded hypersensitivity vasculitis in 74%:

- palpable purpura (usually of buttocks & legs)

- bowel angina

- GI bleed

- hematuria

- onset < 20 years

- no new medications

Essential cryoglobulinemic vasculitis. Most often due to hepatitis C infection, immune complexes of cryoglobulins --- proteins that consists of immunoglobulins and complement and precipitate in the cold while dissolving upon rewarming --- are deposited in walls of capillaries, venules, or arterioles. Therefore, complement will be low with histology showing vessel inflammation with immune deposits.

Granulomatosis with polyangiitis (GPA; formerly known as Wegener's granulomatosis). Systemic vasculitis of medium and small arteries, including venules and arterioles. Produces granulomatous inflammation of the respiratory tracts and necrotizing, pauci-immune glomerulonephritis. Most common cause of saddle nose deformity in USA (nose flattened due to destruction of nasal septum by granulomatous inflammation). Almost all patients with WG have c-ANCA, but not vice versa. Current treatment of choice is cyclophosphamide. At least 2 out of 4 criteria yields sensitivity and specificity of 88 and 92%.

- nasal or oral inflammation (oral ulcers or purulent/bloody nasal discharge, may be painful)

- abnormal CXR showing nodules, infiltrates, cavities

- microscopic hematuria or RBC casts

- vessel biopsy shows granulomatous inflammation

- Peak incidence: ages 40–60, males > females

Eosinophilic granulomatosis with polyangiitis (EGPA; formerly known as Churg-Strauss syndrome). Affects medium and small vessels with vascular and extravascular granulomatosis. Classically involves arteries of lungs and skin, but may be generalized. At least 4 criteria yields sensitivity and specificity of 85 and 99.7%.

- asthma (history of wheezeing or presently wheezing)

- eosinophilia > 10% on CBC

- mononeuropathy or polyneuropathy

- migratory or transient pulmonary opacities on chest x-ray (CXR)

- paranasal sinus abnormalities

- vessel biopsy showing eosinophils in extravascular areas

Microscopic polyarteritis/polyangiitis. Affects capillaries, venules, or arterioles. Thought to be part of a group that includes granulomatosis with polyangiitis since both are associated with ANCA and similar extrapulmonary manifestations. Patients do not usually have symptomatic or histologic respiratory involvement.