The Koebner phenomenon, also called the "Koebner response" or the "isomorphic response", refers to skin lesions appearing on lines of trauma. The Koebner phenomenon may result from either a linear exposure or irritation. Conditions demonstrating linear lesions after a linear exposure to a causative agent include: molluscum contagiosum

Molluscum contagiosum

Molluscum contagiosum is a viral infection of the skin or occasionally of the mucous membranes. It is caused by a DNA poxvirus called the molluscum contagiosum virus . MCV has no animal reservoir, infecting only humans. There are four types of MCV, MCV-1 to -4; MCV-1 is the most prevalent and...

, wart

Wart

A wart is generally a small, rough growth, typically on a human’s hands or feet but often other locations, that can resemble a cauliflower or a solid blister. They are caused by a viral infection, specifically by human papillomavirus 2 and 7. There are as many as 10 varieties of warts, the most...

s and toxicodendron dermatitis (a dermatitis

Dermatitis

-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...

 caused by a genus of plants including poison ivy

Poison ivy

Toxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...

). Warts and molluscum contagiosum lesions can be spread in linear patterns by self-scratching ("auto-inoculation"). Toxicodendron dermatitis lesions are often linear from brushing up against the plant. Causes of the Koebner phenomenon that are secondary to scratching rather than an infective or chemical cause include vitiligo

Vitiligo

Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...

, psoriasis

Psoriasis

Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...

, lichen planus

Lichen planus

Lichen planus is a chronic mucocutaneous disease that affects the skin, tongue, and oral mucosa. The disease presents itself in the form of papules, lesions, or rashes. Lichen planus does not involve lichens, the fungus/algae symbionts that often grow on tree trunks; the name refers to the dry and...

, lichen nitidus

Lichen nitidus

Lichen nitidus is a chronic inflammatory disease of unknown etiology characterized by 1-2 mm, discrete and uniform, shiny, flat-topped, pale flesh-colored or reddish-brown papules that may appear as hypopigmented against dark skin. Occasionally, minimal scaling is present or can be induced by...

, pityriasis rubra pilaris

Pityriasis rubra pilaris

Pityriasis rubra pilaris refers to a group of chronic disorders characterized by reddish orange, scaling plaques and keratotic follicular papules...

, and keratosis follicularis

Keratosis follicularis

Keratosis follicularis may refer to:* Darier's disease* Focal palmoplantar keratoderma with oral mucosal hyperkeratosisSee also:* Isolated dyskeratosis follicularis* Keratosis follicularis spinulosa decalvans...

 (Darier disease).

The Koebner phenomenon describes skin lesions which appear at the site of injury. It is seen in:

• Psoriasis
  Psoriasis
  Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
  
  
• Pityriasis rubra pilaris
  Pityriasis rubra pilaris
  Pityriasis rubra pilaris refers to a group of chronic disorders characterized by reddish orange, scaling plaques and keratotic follicular papules...
  
  
• Lichen planus
  Lichen planus
  Lichen planus is a chronic mucocutaneous disease that affects the skin, tongue, and oral mucosa. The disease presents itself in the form of papules, lesions, or rashes. Lichen planus does not involve lichens, the fungus/algae symbionts that often grow on tree trunks; the name refers to the dry and...
  
  
• Lichen nitidus
  Lichen nitidus
  Lichen nitidus is a chronic inflammatory disease of unknown etiology characterized by 1-2 mm, discrete and uniform, shiny, flat-topped, pale flesh-colored or reddish-brown papules that may appear as hypopigmented against dark skin. Occasionally, minimal scaling is present or can be induced by...
  
  
• Vitiligo
  Vitiligo
  Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...
  
  
• Lichen sclerosus
  Lichen sclerosus
  Lichen sclerosus is an uncommon disease of unknown cause that results in white patches on the skin, which may cause scarring on and around genital skin....
  
  
• Elastosis perforans serpiginosa
  Elastosis perforans serpiginosa
  Elastosis perforans serpiginosa is a unique perforating disorder characterized by transepidermal elimination of elastic fibers and distinctive clinical lesions, which are serpiginous in distribution and can be associated with specific diseases.- References :...
  
  
• Kaposi sarcoma

A similar response occurs in pyoderma gangrenosum

Pyoderma gangrenosum

Pyoderma gangrenosum is a disease that causes tissue to become necrotic, causing deep ulcers that usually occur on the legs. When they occur, they can lead to chronic wounds. Ulcers usually initially look like small bug bites or papules, and they progress to larger ulcers. Though the wounds...

 and Adamantiades-Behcet's syndrome, and is referred to as pathergy.

Warts and molluscum contagiosum are often listed as causing a Koebner reaction, but this is by direct inoculation of viral particles.

Namesake dermatologist

The Koebner phenomenon was named after a rather eccentric, renowned German dermatologist, Heinrich Koebner

Heinrich Koebner

Heinrich Koebner ; was a German dermatologist born in Breslau.He studied medicine in Berlin, earning his doctorate in 1859 at Breslau. Afterwards he performed hospital duties in Vienna under Ferdinand von Hebra and in Paris with Alfred Hardy...

 (1838–1904). Koebner is best known for his work in mycology

Mycology

Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

. Here is one story to illustrate his intense nature: in a medical meeting he proudly exhibited on his arms and chest three different fungus infections, which he self-inoculated in order to prove the infectiousness of the organisms he was studying. The Koebner phenomenon was the generalized term applied to his discovery that on psoriasis patients new lesions often appear on lines of trauma, which are often linear.

Contrasted distributions

The linear arrangement of skin lesions in the Koebner phenomenon can be contrasted to both lines of Blaschko and dermatomal distributions. Blaschko lines follow embryotic cell migration patterns and are seen in some mosaic genetic disorders such as incontinentia pigmenti

Incontinentia pigmenti

Incontinentia Pigmenti is a genetic disorder that affects the skin, hair, teeth, nails, and central nervous system...

 and pigment mosaicism. Dermatomal distributions

Dermatomic area

A dermatome is an area of skin that is mainly supplied by a single spinal nerve.There are eight cervical nerves ,twelve thoracic nerves,five lumbar nerves and five sacral nerves....

 are lines on the skin surface following the distribution of spinal nerve roots. The rash caused by herpes zoster (Shingles) follows such dermatomal lines.

Sources

• Crissey JT, Parish LC, Holubar KH. Historical Atlas of Dermatology and Dermatologists. New York: The Parthenon Publishing Group, 2002.
• Paller A, Mancini A. Hurwitz Clinical Pediatric Dermatology. Pilladelphia: Elsevier Saunders, 2002.