AGEP is an acute febrile drug eruption characterized by numerous small, primarily non-follicular, sterile pustules, arising within large areas of red swollen skin.

The eruption follows a self-limiting course and will end before a week provided the causative agent (e.g. medication) is discarded. It is accompanied by fever, a high number of neutrophils and eosinophils in the blood, liver inflammation, and sometimes by facial swelling. The mortality rate is about 5% and the differential diagnosis includes Stevens–Johnson syndrome (SJS). Contrary to SJS, in AGEP, mucosa are not affected, which means that there are no blisters in the mouth or vagina.

The treatment is (1) stop the offending drug (antibiotics), (2) symptomatic (fever), and (3) for complications (hepatitis).

Characteristics may vary according to the subtype of pustular psoriasis. For example, it can be localized, commonly to the hands and feet (localized pustular psoriasis), or generalized with widespread patches occurring randomly on any part of the body (generalized pustular psoriasis). However, all forms of pustular psoriasis share in common the presence of red and tender blotchy skin covered with pustules.

Pustular psoriasis can be localized, commonly to the hands and feet (palmoplantar pustulosis), or generalized with widespread patches occurring randomly on any part of the body. Acrodermatitis continua is a form of localized psoriasis limited to the fingers and toes that may spread to the hands and feet. Pustulosis palmaris et plantaris is another form of localized pustular psoriasis similar to acrodermatitis continua with pustules erupting from red, tender, scaly skin found on the palms of the hands and the soles of the feet.

Generalized pustular psoriasis (GPP) is also known as (von Zumbusch) acute generalized pustular psoriasis in acute cases, and as impetigo herpetiformis during pregnancy. GPP is a rare and severe form of psoriasis that may require hospitalization. This form of psoriasis is characterized by an acute onset of numerous pustules on top of tender red skin. This skin eruption is often accompanied by a fever, muscle aches, nausea, and an elevated white blood cell count. Annular pustular psoriasis (APP), a rare form of GPP, is the most common type seen during childhood. APP tends to occur in women more frequently than in men, and is usually less severe than other forms of generalized pustular psoriasis such as impetigo herpetiformis. This form of psoriasis is characterized by ring-shaped plaques with pustules around the edges and yellow crusting. APP most often affects the torso, neck, arms, and legs.

Id reactions (also known as "disseminated eczema," and "generalized eczema") are types of acute dermatitis developing after days or weeks at skin locations distant from the initial inflammatory or infectious site. They can be localised or generalised. This is also known as an 'autoeczematous response' and there must be an identifiable initial inflammatory or infectious skin problem which leads to the generalised eczema. Often, intensely itchy, the red papules and pustules can also be associated with blisters and scales and are always remote from the primary lesion. It is most commonly a blistering rash with itchy vesicles on the sides of fingers and feet as a reaction to fungal infection on the feet, athlete's foot. Stasis dermatitis, Allergic contact dermatitis, Acute irritant contact eczema and Infective dermatitis have been documented as possible triggers, but the exact cause and mechanism is not fully understood. Several other types of id reactions exist including erythema nodosum, erythema multiforme, Sweet's syndrome and urticaria.

Causes include infection with dermatophytosis, Mycobacterium, viruses, bacteria and parasites. Eczematous conditions including contact allergic dermatitis and stasis dermatitis as well as stitches and trauma have also been associated with id reactions. Radiation treatment of tinea capitis has been reported as triggering an id reaction.

GPP presents as pustules and plaques over a wide area of the body. It differs from the localized form of pustular psoriasis in that patients are often febrile and systemically ill.

However, the most prominent symptom, as described in the "Archives of Dermatology", is “sheeted, pinhead-sized, sterile, sub-corneal pustules”. The IPC roundtable adds that these pustules often occur either at the edges “of expanding, intensely inflammatory plaques” or “within erythrodermic skin.”

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

GPP is a rare and severe type of psoriasis. It in rare cases it is said to be fatal and in some cases has driven patients to intensive burn units. An article published in "Pediatric Dermatology" said, “The GPP pattern is as an acute, episodic, and potentially life-threatening form of psoriasis.”

There is no cure-all treatment for GPP, and as such, the mortality rate is high. Ryan and Baker observed 155 patients with GPP, 106 of which were followed up with. 26 of those 106 died as a result of the psoriasis or the treatment. Their data gives a 25% mortality rate.

There are many cases where GPP has been treated or reduced to a manageable level. The treatments vary depending on the specific factors of each case.

Neonatal toxic shock-like exanthematous disease is a cutaneous condition characterized by a generalized diffuse macular erythema or morbilliform eruption with confluence.

Localized pustular psoriasis presents as two distinct conditions that must be considered separate from generalized psoriasis, and without systemic symptoms, these two distinct varieties being pustulosis palmaris et plantaris and acrodermatitis continua.

Generalized vaccinia is a cutaneous condition that occurs 6–9 days after vaccination, characterized by a generalized eruption of skin lesions, and caused by the vaccinia virus.

This infection affects multiple organs, including the eyes, brain, lung, and liver, and can be fatal.

Pustulosis is highly inflammatory skin condition resulting in large fluid-filled blister-like areas - pustules. Pustulosis typically occurs on the palms of the hands and/or the soles of the feet. The skin of these areas peels and flakes (exfoliates).

This condition—also referred to as "palmo-plantar pustulosis"—is a feature of pustular psoriasis.

Patients with acute GPP experience the eruption of multiple isolated sterile pustules generalized over the body, recurrent fevers, fatigue, and laboratory abnormalities (elevated ESR, elevated CRP, combined with leukocytosis).

Eczema herpeticum is a rare but severe disseminated infection that generally occurs at sites of skin damage produced by, for example, atopic dermatitis, burns, long term usage of topical steroids or eczema. It is also known as Kaposi varicelliform eruption, Pustulosis varioliformis acute and Kaposi-Juliusberg dermatitis.

Some sources reserve the term "eczema herpeticum" when the cause is due to human herpes simplex virus, and the term "Kaposi varicelliform eruption" to describe the general presentation without specifying the virus.

This condition is most commonly caused by herpes simplex virus type 1 or 2, but may also be caused by coxsackievirus A16, or vaccinia virus. It appears as numerous umbilicated vesicles superimposed on healing atopic dermatitis. it is often accompanied by fever and lymphadenopathy. Eczema herpeticum can be life-threatening in babies.

The most common type of eruption is a morbilliform (resembling measles) or erythematous rash (approximately 90% of cases). Less commonly, the appearance may also be urticarial, papulosquamous, pustular, purpuric, bullous (with blisters) or lichenoid. Angioedema can also be drug-induced (most notably, by angiotensin converting enzyme inhibitors).

Eosinophilic folliculitis (also known as "Eosinophilic pustular folliculitis" and "Sterile eosinophilic pustulosis") is an itchy rash with an unknown cause that is most common among individuals with HIV, though it can occur in HIV-negative individuals where it is known by the eponym Ofuji disease. EF consists of itchy red bumps (papules) centered on hair follicles and typically found on the upper body, sparing the abdomen and legs. The name eosinophilic folliculitis refers to the predominant immune cells associated with the disease (eosinophils) and the involvement of the hair follicles.

Eosinophilic folliculitis associated with HIV infection typically affects individuals with advanced HIV and low T helper cell counts. It affects both men and women as well as children with HIV and is found throughout the world.

EF may also affect individuals with hematologic disease such as leukemia and lymphoma. It may also affect otherwise normal infants in a self-limited form. HIV-negative individuals can also develop EF — this is more common in Japan.

Pustulosis palmaris et plantaris (also known as pustulosis of palms and soles, palmoplantar pustulosis, persistent palmoplantar pustulosis, pustular psoriasis of the Barber type, and pustular psoriasis of the extremities) is a chronic recurrent pustular dermatosis (that is, a pustulosis or pustular psoriasis) localized on the palms and soles only, characterized histologically by intraepidermal pustules filled with neutrophils. It can occur as part of the SAPHO syndrome.

Kogoj's spongiform pustules can be observed via histopathology to confirm acute GPP.

"Distribution" refers to how lesions are localized. They may be confined to a single area (a patch) or may exist in several places. Some distributions correlate with the means by which a given area becomes affected. For example, contact dermatitis correlates with locations where allergen has elicited an allergic immune response. Varicella zoster virus is known to recur (after its initial presentation as chicken pox) as herpes zoster ("shingles"). Chicken pox appears nearly everywhere on the body, but herpes zoster tends to follow one or two dermatomes; for example, the eruptions may appear along the bra line, on either or both sides of the patient.

- Generalized

- Symmetric: one side mirrors the other

- Flexural: on the front of the fingers

- Extensor: on the back of the fingers

- Intertriginous: in an area where two skin areas may touch or rub together

- Morbilliform: resembling measles

- Palmoplantar: on the palm of the hand or bottom of the foot

- Periorificial: around an orifice such as the mouth

- Periungual/subungual: around or under a fingernail or toenail

- Blaschkoid: following the path of Blaschko's lines in the skin

- Photodistributed: in places where sunlight reaches

- Zosteriform or dermatomal: associated with a particular nerve

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.

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.

Some of the most severe and life-threatening examples of drug eruptions are erythema multiforme, Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), hypersensitivity vasculitis, Drug induced hypersensitivity syndrome (DIHS), erythroderma and acute generalized exanthematous pustulosis (AGEP). These severe cutaneous drug eruptions are categorized as hypersensitivity reactions and are immune-mediated. There are four types of hypersensitivity reactions and many drugs can induce one or more hypersensitivity reactions.

Acropustulosis refers to Acrodermatitis with pustular involvement.

Types include:

- Pustulosis palmaris et plantaris

- Infantile acropustulosis