1. One of a group of chronic, relapsing autoimmune skin diseases that cause blisters and erosions of the skin and mucous membranes.

The immune system mistakenly regards the cells in the skin and mucous membranes as foreign and attacks them.

2. A distinctive group of skin and mucous membrane diseases, characterized by successive skin eruptions of crops of bullae (large blisters or vesicles which are serum-filled blisters formed in or beneath the skin).
3. An acute or chronic autoimmune disease principally of adults but sometimes found in children, characterized by an occurrence of successive crops of bullae that appear suddenly on apparently normal skin and disappear, leaving pigmented spots.

A characteristic sign is a positive Nikolsky's sign: when pressure is applied to an area as if trying to push the skin parallel to the surface, the skin will detach from the lower layers.

Nikolsky's sign is also described as a peculiar vulnerability of the skin in pemphigus vulgaris; where the apparently normal epidermis may be separated at the basal layer and rubbed off when pressed with a sliding motion.

Pyotr Nikolsky (1858-1940) was a Russian dermatologist.

A diagnostic feature wherein apparently normal epithelium may be rubbed off with pressure.

One simple way to perform this test is with a pencil. With the eraser side of a pencil down, the pencil is firmly placed on the skin and depressed while twisted.

If the patient has one of a number of vesicular (blister)/bullous (bump filled with fluid) diseases, he or she will test positive for Nikolsky's sign, and a blister will form within a matter of minutes.

The histologic basis for the sign

The idea behind this test lies in the histologic properties of certain vesicular/bullous diseases. In these diseases, there are defects in the cell-to-cell attachment mechanisms, and even very small amounts of trauma can elicit a clinical response of a blister formation when the cells are manually detached with the forceful turn of the pencil eraser on the skin.

In the case of pemphigus, the pencil twist easily rips the spinous cells apart because they possess defective desmosomes, and in the case of pemphigoid, the hemidesmosomes (specialised structure that attaches an epithelial cell, or outside layer of a cell, to the basement membrane beneath it) are defective.

Within minutes, a blister will form, and this is pathognomonic, or absolutely indicative, of a vesicular/bullous disease.

A nonspecific term for blistering skin diseases: "The renowned dermatologist assured the patient with the blisters on her face that she had a form of benign (harmless) familial chronic pemphigus."

Scaling, erythematous macules and blebs of the scalp, face, and trunk.

The lesions (breaks) have a "butterfly" distribution over the face. The disease resembles pemphigus foliaceus.

Erythematous refers to redness of the skin caused by congestion of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation.

Macules concerns small flat blemishes or discolorations that are level with the surface of the skin.

Blebs are small blisters or bubbles.

An uncommon vesicular dermatitis endemic in tropical areas, primarily affecting the armpits and the groin.

An eruption involving sun-exposed skin; especially, the face.

The lesions are scaling erythematous macules and blebs, combining the clinical features of both lupus erythematosus and pemphigus vulgaris.

Pemphigus with a chronic course and in which bullous lesions may be absent.

Once lesions develop they may spread to the entire body and mimic generalized exfoliative dermatitis (scaling and itching of the skin and the loss of hair). The positive Nikolsky's sign helps to make the correct diagnosis.

A pyoderma or a skin infection causing the development of pus or pustules (small, inflamed, pus-filled, blister-like lesions on the skin surface) particularly in tropical climates.

A form of pemphigus vulgaris characterized by pustules (small raised areas on the skin which contain pus) instead of bullae (large blisters).

Pustules are followed by warty vegetations (outgrowths) on the denuded areas of the skin rather than healing normally.

The most common form of pemphigus.

This is a group of important skin conditions and their principal feature is the formation of multiple large blisters in the skin and mouth that burst easily.

The conditions are rare; slightly more women are affected than men. They constitute a dermatological emergency and patients will need hospital treatment.

It is believed that the cause is auto immune; that is, the bodies own defense mechanism wrongly attacks these tissues and creates the illness; apparently because the immune system mistakenly regards the cells in the skin and mucous membranes as foreign cells and attacks them.

Patients require expert care and are at risk of body chemistry disturbances and infection as the blisters easily burst and leave open wounds and the lesions have little tendency to heal.

Currently the primary treatment is to suppress the body's own immune system using powerful drugs.