What Is Koebner Phenomenon

The Koebner phenomenon is associated with underlying skin conditions, like psoriasis and vitiligo. It is characterised by secondary lesions resulting from triggering factors, such as injuries, chemical reactions, and mechanical stressors like continuous pressure and friction. The new lesions have the same characteristics as the primary skin condition. In other words, lesions corresponding to the underlying skin condition are developed in previously unaffected areas. 

The Koebner phenomenon refers to the development of new cutaneous lesions characteristic of a pre-existing skin condition, such as psoriasis and vitiligo. These lesions compromise previously unaffected skin areas and are commonly induced by triggering factors, including skin trauma. 

Overview

The skin is the largest organ in the human body. It constantly interacts with the external world, including temperature, chemicals, microorganisms, allergens, and mechanical factors like pressure and friction. Our simultaneous interaction with the environment influences skin homeostasis, a state of balance. However, the pathways involved in mechanisms that govern essential functions, including the body’s capacity for healing, get impaired in some skin conditions.¹

The Koebner phenomenon (KP), also known as the isomorphic phenomenon, refers to the appearance of new cutaneous lesions characteristic of a pre-existing dermatologic disease.^2–4 These new lesions can be triggered by various factors, including traumatic injuries, sustained friction and pressure, scars, exposure to ultraviolet radiation, and even tattoos.

This phenomenon was first described in 1876 by Heinrich Koebner, a German dermatologist who noticed the formation of new psoriatic lesions after skin trauma in patients with psoriasis.^3,4 Since then, many other associated skin conditions have been recognised, primarily those with an inflammatory autoimmune and chronic nature, such as psoriasis, vitiligo, and lichen planus.

The overall prevalence of KP is unknown. Some studies suggest it is observed in around 5% to 61% of vitiligo patients and 25% to 30% of psoriasis patients after skin trauma.^2,3 Conversely, other studies suggest rates from 21% to 62% in vitiligo and 11% to 75% in psoriasis.⁵ Furthermore, a study by Sharma and collaborators observed that almost 30% of 50 patients with lichen planus reported KP.² Some report cases have been published in less frequent scenarios, such as lupus with skin involvement and repetitive trauma from insulin injection for diabetes treatment.⁶

Causes of Koebner phenomenon

The causes of KP are not fully understood. Several theories exist, including abnormal immune responses, vascular processes involving blood vessels, neural components from the nervous system, and hormonal reactions. However, none of these theories has been definitively confirmed, and a combination of mechanisms is likely at play.^1,2

It’s worth noting that some drugs, like lithium for psychiatric disorders, beta blockers for heart conditions, and certain anti-inflammatory medications, have been associated with exacerbating conditions like psoriasis, leading to KP through chemical contact.³ On the contrary, insulin injections have been reported due to repetitive trauma to the skin surface.⁷

Similar reactions, known as the pseudo-Koebner phenomenon, can be observed on skin infections (for example, viral warts) after manipulation, promoting spread across the skin. 

Signs and symptoms of Koebner phenomenon

KP typically involves the development of new, identical lesions from the primary skin condition in previously unaffected areas. This phenomenon can occur at any stage of the disease, whether shortly after diagnosis or years later.

Furthermore, KP can affect any body part, but usually appears in the injured area. The timeline for KP development varies from patient to patient. Some studies report an average of 10 to 20 days after the initial insult, whereas others mention around 1–2 months after injury. No specific period has been established to differentiate between late KP and non-KP-related lesions.²

Management and treatment for Koebner phenomenon

Managing KP involves controlling the underlying skin condition by implementing treatments and lifestyle modifications. It’s crucial to understand that KP is associated with poorer treatment responses and rapid progression, so continuous evaluation of disease activity and treatment effectiveness is essential.

Furthermore, the patient must understand which lesions can promote KP’s development to prevent trauma as much as possible. Any injury penetrating your skin’s top and middle layers, known as the epidermis and dermis, can cause KP. These include injections, piercings, punctures like acupuncture, insect and animal bites, scratching, skin picking, wounds, burns, surgical procedures, tattoos, lasers, and ultraviolet radiation.² 

Diagnosis

The diagnosis of KP is based on medical history and physical examination. In other words, KP has no specific diagnostic test, and the diagnosis relies on clinicians.

Risk factors

Risk factors for developing KP involve skin trauma, especially within pre-existing inflammatory skin conditions.

Triggering factors encompass a broad spectrum, ranging from physical trauma such as injuries, burns, freezing, the application of tattoos, and exposure to ultraviolet radiation. Furthermore, chemical stimulation, often induced by contact with certain substances, including drugs or insect bites, can contribute to this phenomenon. Mechanic stress, including scratching, sustained pressure, and friction, has also been identified as a factor. In healthcare scenarios, medical interventions like vaccination, injections, laser hair removal, needle acupuncture, and intravenous infusions can potentially exacerbate lesions.^2,4,7

Trauma is the most frequent associated trigger. Interestingly, not all types of injuries induce KP in the same patient. Additional factors, including depth, width, duration, affected area and type of trauma, play a vital role in the development of KP.² 

FAQs

How can I prevent Koebner phenomenon

The most efficient ways to prevent Koebner phenomenon include controlling the primary disease and preventing skin trauma. Avoid contact sports and high risk activities, sunburns, aesthetic procedures like laser hair removal and waxing, and complementary medical therapies like acupuncture. It is important to note that not all stimuli will produce associated lesions in all patients. 

How common is Koebner phenomenon

The prevalence of KP varies among populations and underlying skin disorders. However, it is estimated to affect around 25% of patients with psoriasis at some stage along the disease’s course. 

When should I see a doctor

If Koebner phenomenon is suspected, it is worth consulting your physician because it is associated with disease flare-ups and poorer outcomes, including suboptimal treatment response and rapid progression. Other signs and symptoms that must be addressed include severely painful or itchy skin, severe wounds, and signs of infection, including fever, chills, and general malaise. 

Summary

The Koebner phenomenon is characterised by developing new lesions from pre-existing skin conditions most commonly triggered by trauma and procedures. Its cause is not well understood and requires further investigation. Diagnosis relies on the medical history and physical examination by a physician. It is essential to recognise KP since it is associated with poorer outcomes, including disease activity, suboptimal treatment response, and a rapid disease course. Treatment consists of managing the primary disease and preventing skin trauma that could induce lesions. If present, the secondary lesions must be handled in the same way as the primary skin disorder.