Koebner Phenomenon and Pseudo-Koebner Phenomenon Due to Disposable Surgical Masks in the Covid Era.

Sir,

Koebner phenomenon (KP) refers to the appearance of lesions similar to that of a pre-existing dermatologic condition on normal skin induced by trauma, seen commonly in psoriasis, and vitiligo. Pseudo-Koebner phenomenon (PKP) is the induction of new lesions due to traumatic seeding of infective material into the normal skin from a pre-existing focus most commonly noticed in viral warts or Mollusca.[1] Regular and diligent use of various types of masks is one of the most important, effective, and inexpensive measures to prevent the spread of COVID-19 and other infections.[2] A number of facial skin conditions have purportedly been induced by prolonged use of these masks. These include pressure- or friction-induced changes (impression marks, erosions/ulcerations, crusting), erythema, dryness, contact dermatitis (irritant/allergic), itching, and appearance of new or exacerbation of existing facial dermatoses such as acne, rosacea, seborrheic dermatitis, and tinea.[34]

Mask-induced KP and PKP are not very commonly reported entities although this may have been seen in the current COVID-19 pandemic due to regular prolonged use of masks. We report here two cases, one showing KP due to mask in a patient with psoriasis, and the other patient having viral warts exhibiting PKP.

Case 1: A 30-year-old man, working as a clerk and having localized psoriasis on the knees, elbows, and glans penis (Body surface area (BSA) < 10%) for 2 years developed typical erythematous silver scaly psoriatic plaque on the left supra-auricular groove 2 months ago [Figure 1]. The patient's psoriasis had been under control and stable with topical treatment and emollient application. There was no joint pain or nail involvement.

Figure 1

Psoriatic plaque on the left supra-auricular groove due to mask loop (Koebner phenomenon)

Case 2: A 35-year-old man, working as a cashier in a supermarket, had a single verruca on the right side of his scalp for 6 weeks. He developed multiple similar flat lesions in a linear band on the area of the scalp, and the superior part of the right pinna coming in contact with the mask string [Figure 2]. The lesions were removed by electrofulguration without any scarring, recurrence, or seeding.

Figure 2

Multiple flat warts on the superior part of the right pinna and adjoining scalp due to mask string (pseudo–Koebner phenomenon)

Both patients had been using disposable surgical masks daily for months as protection against COVID-19 infection. There was no history of using spectacles/goggles/any headgear by both the patients.

The eponymous phenomenon KP bearing the name of Heinrich Koebner was first described by him in 1872 in psoriasis patients.[1] A wide variety of external and internal stimuli such as physical damage, infections, light, vaccines, irritant/allergic reactions, and drugs, have been implicated. A large number of skin conditions have been reported to exhibit KP and PKP. The exact etiopathogenesis is not known. The extent, depth, type, and severity of injury determine the occurrence and severity of KP. Both epidermal and dermal components injuries are needed.[1]

Since the SARS CoV-2-induced COVID-19 disease appeared in China in December 2019, it became a global pandemic within a few months, and reports started appearing documenting the occurrence of skin-related signs, symptoms, conditions, and diseases induced by various personal protective equipment (PPE), especially different types of masks (N95 masks, surgical disposable, and cloth masks), goggles, face shields, etc., and preventive hygiene practices mandated to be used among the health care workers (HCW).[34] Among the first reports of its kind, 97% of the HCW had some kind of skin condition induced by these PPE.[3] The nasal bridge, cheeks, chin were the most commonly affected sites. The most common conditions reported due to the use of masks in HCW were those caused by pressure injury (impression/indentation marks, ulcerations, erosions, and crusting), pressure urticaria, and exacerbation of pre-existing skin condition (acne, seborrheic dermatitis).[3] Frictional dermatitis, irritant contact dermatitis (CD) (redness, scaling), lip lick dermatitis, exacerbation of acne, seborrheic dermatitis, tinea was reported in a similar study from India.[4] The change in temperature, hydration, sebum secretion, occlusion, excessive pressure, friction by mask, and allergic contact dermatitis from the mask material including itching are the common factors speculated to have played a role. The duration of wearing masks (>6 h) was the most significant factor.[234]

However, there have been a few reports on the occurrence of KP or PKP due to masks in general public or non-admitted COVID-19 patients until recently.[56]

A recently published large multicentric study found that 26.2% (229/873) of all the dermatological consultations (in-person/online) had KP due to masks.[6] Ear lobes, malar area, and perioral nose were the most common sites affected. One hundred forty-two patients exhibited true KP (37 psoriasis, 14 vitiligo, 64 maskne, 26 mask rosacea) and 24 had PKP (11 warts, 4 mollusca, 9 impetigo).[6] Mask tinea has also been described to precipitate or exacerbate due to regular mask use.[7]

Our first patient of psoriasis developed a psoriatic lesion as KP on the supra-auricular grove of the pinna due to pressure/friction from the loop of the mask as reported by Mutalik et al.[5] The second case demonstrated PKP due to mask. In the largest study on mask-induced KP, psoriasis was the most common condition among adults, followed by vitiligo and lichen planus. Supra-auricular groove was found to be the most common site exhibiting KP; PKP was evoked by a looped mask.[6]

The regular, consistent, and conscientious use of masks is one of the most important, effective, and inexpensive measures to prevent the spread of dreaded COVID-19 and other infections. These two cases highlight the need for awareness of the possibility of masks/similar equipment inducing Koebnerization or PKP and perpetuation/aggravation of skin lesions requiring innovative ways to prevent such eventuality.

A number of measures have been suggested to avoid mask-induced skin conditions. They may help in preventing KP/PKP in the patients. Their knowledge, awareness, and suggestion by the treating physicians to the patients can help prevent the development of KP/PKP. These include simple measures such as padding the loop area with soft cotton or tissue papers and applying emollients, use of acrylate lotion and protective acrylate layers, avoiding latex loops, and tying the loop over the scalp.[56] Maintaining adequate hydration, frequent breaks, prophylactic dressings, gentle skincare, use of emollients, and newly designed better-fitting masks can help reduce the occurrence of mask-induced dermatoses among the general public and HCW.[2]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.