What is the Koebner phenomenon?
The Koebner phenomenon describes the appearance of new skin lesions on areas of cutaneous injury in otherwise healthy skin. It is also known as the isomorphic response.
How is the Koebner phenomenon diagnosed?
Lesions arising through the Koebner phenomenon:
- Develop at sites of cutaneous injury (such as a scratch), in previously healthy skin
- Have the same clinical and histological features as lesions of the patient's original skin disease
- Are not due to the seeding of an infectious agent, an allergic reaction to a contact agent, or skin breakdown.
Lesions may form in patients with or without pre-existing skin conditions. A true Koebner response can be confirmed by experimentally reproducing lesions with different methods of injury. However this may not always work and is not usually practical or desirable.
Koebner phenomenon lesions are often linear in shape, as they follow the route of cutaneous injury. Aside from linear skin injury, linear lesions arising from the Koebner phenomenon can also be seen in mosaic skin disorders (eg segmental lichen planus).
Features of the Koebner phenomenon
Graded response to trauma
Patients will differ in terms of how intensely they respond to skin injury:
- Maximal Koebner response: lesions develops across the entire injured area
- Minimal Koebner response: lesion develops in focal areas of trauma
- Abortive Koebner response: lesions appear, but spontaneously vanish after 12–20 days
- No Koebner response to injury
“All or nothing” response
Patients who develop Koebner phenomenon in response to one method of injury are susceptible to other triggering stimuli. This is particularly noted in patients with psoriasis. Conversely, a patient who does not develop skin lesions with one type of injury is not expected to exhibit Koebner phenomenon with another type of injury.
Time to development of lesions
The time from injury to formation of a skin lesion depends on the specific skin disease. For psoriatic lesions (these are known as plaques), it is between 10 to 20 days, with a range from 3 days to 2 years. The time to lesion formation can differ in the same patient.
Non-cutaneous Koebner phenomenon
Some reports suggest the Koebner phenomenon may affect other surfaces apart from the skin, such as the oral mucosa, or cause lesions in internal organs, such as the lungs after damage from chronic infection. It is uncertain whether it occurs in systemic diseases such as sarcoidosis and systemic lupus erythematosus. Cutaneous lesions due to Koebner phenomenon have been reported in these diseases.
Other phenomena in relation to trauma or skin damage are distinct from the Koebner phenomenon:
- Reverse Koebner phenomenon: the disappearance of a skin lesion after trauma to the area
- Wolf's isotopic response: the emergence of new lesions in the exact place of previous, healed, lesions not necessarily due to trauma
- Renbok phenomenon: the disappearance of an existing dermatosis after the onset of a new lesion at the same location
- Pathergy: altered tissue reactivity in response to trauma, with formation of papules or pustules
Triggers of Koebner phenomenon
|True Koebner response|
|Occasional, localised traumatic lesions|
A variety of skin injuries have been found to trigger the Koebner phenomenon (table 2).
|Diseases/ medical conditions||
What is the cause of Koebner phenomenon?
The cause of the Koebner phenomenon is unclear. Current theories suggest the Koebner phenomenon requires both epidermis and dermis to be injured at the same site. The production of inflammatory substances and neuropeptides has been postulated as a non-specific first step, triggering a secondary disease-specific process. The role of chemical messengers such as nerve growth factor (NGF) may be important and is being investigated.
Koebner phenomenon in psoriasis
Psoriasis is the most-researched condition that exhibits the Koebner phenomenon, and can be used to aid diagnosis.
Koebner phenomenon has been noted to be particularly prevalent in:
- Unstable psoriasis
- Patients with a young age of onset of psoriasis
- Patients who have received multiple treatments for psoriasis
- Winter, compared to summer
- Emotionally distressed patients
Other studies indicate that Koebner phenomenon:
- Occurs less frequently during remission of psoriasis
- Is not related to disease severity; can occur in mild and severe disease
- Is not related to disease activity
Plaques exhibiting the Koebner phenomenon can appear on any area of the body, even those not usually involved by psoriasis.
In recalcitrant psoriasis, a concurrent skin condition such as contact dermatitis may drive the disease via the Koebner phenomenon.
Koebner phenomenon in psoriasis
Can Koebner phenomenon be prevented?
Although it is not possible to prevent all cutaneous injury, if you are susceptible to the Koebner phenomenon, take care to avoid:
The following things have been experimentally suggested to prevent the Koebner phenomenon:
- Pressure, such as a pressure dressing or bandage
- Suction, such as a vacuum dressing
- Vasoconstrictors, such as adrenaline
What is the treatment for Koebner phenomenon?
- Elective surgery/procedures should be performed while skin disease is stable or in remission
- Active systemic treatment of psoriasis or cutaneous lupus erythematosus may suppress the Koebner phenomenon
- Bland ointment may be inhibitory but topical corticosteroids have not be shown to prevent Koebner phenomenon.
Treatment for cutaneous lesions arising from the Koebner phenomenon depends on the associated skin condition.