During a rapid skin cycle, the dying skin cells build up into often red, scaly patches that can be itchy and painful. Often, the patches develop on the trunk and around the joints.
For some people with psoriasis, patches may form in an area where there has been an injury.
These lesions usually appear within 10 to 20 days but may take as long as 2 to 3 years to develop fully.
- The Koebner phenomenon is a condition that causes lesions to appear near skin injuries.
- There is no way to prevent the Koebner phenomenon entirely.
- It is differentiated according to the severity and presentation of the lesions.
- It may present differently in different people.
What is Koebner phenomenon?
Where there has been an injury to the skin, patches of psoriasis may form.
The Koebner phenomenon is often associated with skin disorders, such as psoriasis. However, individuals who do not have skin problems may also develop Koebner phenomenon.
There are four levels of Koebner phenomenon:
- no Koebner response after injury
- abortive Koebner response occurs but disappears quickly within 10 to 20 days
- minimal Koebner response at the primary points of injury
- maximal Koebner response lesions occur over the entire injured area
A Koebner phenomenon that develops due to one type of injury, such as a cut, is likely to appear as a result of another kind of injury, such as a burn or bite. On the other hand, if a person does not develop a Koebner response from an injury, it is unlikely that it will occur after a different type of injury.
What are the symptoms?
In people with psoriasis, Koebner phenomenon causes psoriasis patches or irritation to develop on or around the injured area. The patches will often be linear or follow the shape of the injury itself in the case of a cut, blister, or insect bite.
How is it caused?
Despite knowing about the phenomenon for well over a century, doctors are still not sure exactly what causes it. What they do know is that the skin is overreacting to a stimulus. Some potential immediate causes include:
- contact with allergens or irritants
- cuts or scrapes
- flares of psoriasis
- injury from bee or insect stings, bites, burns, or bruises
- radiation or sunburn
- winter or periods of cold weather
- times of stress
Some researchers have theories about what causes Koebner phenomenon. For example, some researchers suggest that both layers of skin (the epidermis and dermis) need to be injured at the same time.
Another theory suggests that the inflammatory responses to the injury may trigger psoriasis to develop.
Additionally, the Koebner phenomenon occurs more frequently in people who were diagnosed with psoriasis when they were very young. Interestingly, people rarely report the phenomenon after they have had a vaccine or a tattoo.
What is the link to psoriasis?
Psoriasis patches may form around wounds for those who have psoriasis and experience Koebner phenomenon.
Psoriasis and other skin disorders are associated with higher instances of the Koebner phenomenon.
When psoriasis is present, the lesions that appear with Koebner will look and feel like the other psoriasis patches.
Not all people who have psoriasis will develop Koebner phenomenon.
How are they related?
Koebner phenomenon and psoriasis are distinct conditions. Koebner phenomenon can occur alongside other skin disorders or on its own. However, because psoriasis is a widely studied disease, Koebner phenomenon is often studied in people who have psoriasis.
People with psoriasis who experience Koebner phenomenon will likely develop psoriasis patches around wounds. Often, it will take several days for the new patches to appear, but they may take a few years to form.
Even the most careful person eventually gets a cut or scrape. A person prone to Koebner phenomenon can take precautionary steps, however. Some suggestions include:
- avoiding sunburn by using lotions and staying in the shade
- avoiding potential irritants that cause a skin reaction
- avoiding scratching the skin
There are some ideas for prevention that are still in experimental stages and require additional testing and research. Some potentially effective methods to prevent Koebner phenomenon include:
- suction through use of a vacuum bandage
- pressurized bandaging
- vasoconstrictors - medications that constrict blood flow
When to see a doctor
Medicated creams and ointments may help to treat psoriasis.
Any time a new patch or area of psoriasis develops where it has not before, it is a good idea to see a doctor.
A person can look for signs such as a linear patch forming around the site of a recent injury. In other cases, where the new patch takes months or years to develop, it may be harder to determine the cause.
A doctor will need to examine the person to determine the cause of the new patch.
To make a diagnosis, a doctor will look for the following:
- a linear patch or lesion at the site of a cut or scrape
- a patch that has the same characteristics as psoriasis (or other skin disorder)
- a patch that is not due to the normal spreading of the disease or caused by the skin breaking down
How is it treated?
Treatment for Koebner phenomenon is dependent on the other condition. In the case of psoriasis, some treatment options may include:
- topical treatments, such as medicated creams and ointments
- light therapy
- oral medications
Once a Koebner phenomenon patch appears as a result of one type of injury or cut, it is very likely it will occur again after the same or different injury.
In cases of psoriasis, treatment for the newly-infected area will likely be the same as for the other psoriasis patches. Sometimes, a doctor may recommend additional treatment options, however.
A person who experiences the Koebner phenomenon should take some extra precautions if they find themselves in a situation where the chances of getting a cut or scrape are higher than usual.