Extensive cutaneous lichen planus triggered by viral vector COVID-19 vaccination (ChAdOx1 nCoV-19).

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Since the widespread campaign of COVID-19 vaccination, large retrospective studies reported a broad spectrum of cutaneous reactions after messenger RNA (mRNA) COVID-19 vaccines. Vaccine-triggered cutaneous manifestations seem rare1 and could be related either to the vaccine or to the adjuvant. Overall, cutaneous reactions to mRNA-based COVID-19 vaccines are generally mild and self-limited, consisting mostly of minor local or delayed large site reactions with a female predominance.2 A few cases of lichen planus (LP) were described after Pfizer/BioNTech (New York, NY, USA; BNT162b2) and Moderna (Cambridge, MA, USA; mRNA-1273) vaccines.2-7 We report a case of a new-onset cutaneous LP triggered by another type of vaccination, namely AstraZeneca adenovirus-based vaccine (ChAdOx1 nCoV-19). A 65-year-old-woman presented to our outpatient clinic 2 months after the second injection of ChAdOx1 nCoV-19 vaccine for a 5-month history of itchy eruption. The lesions started ten days after the first injection and worsened seven days after the second, given 3 months apart. The patient had no other medication and no symptoms of viral infection before the immunizations. Physical examination revealed large hyperpigmented plaques on the arms, legs and buttocks on areas affected since the first flare (Fig. 1a). Extensive small, polygonal, erythematous papules that coalesce to form brownish plaques appeared after the second injection were observed on the abdomen and the four limbs (Fig. 1b,c). Dermoscopic examination revealed Wickham striae (Fig. 2). Nails and mucous membranes were spared. Skin biopsy revealed an interface lichenoid dermatitis with mononuclear cells, melanophages, and rare eosinophils infiltrating the superficial dermis. Considering the delay after the vaccination, the positive rechallenge to the vaccine, and the absence of intake for confounder drugs, the patient was diagnosed with a probable drug-induced LP according Naranjo accountability score8 and with an intrinsic accountability of I3 (S2C2) considering Begaud's accountability scores.9 Hepatitis C virus serology was negative. Treatment with clobetasol propionate 0.05% cream led to a nearly complete remission in four weeks. After three months, the patient still experiences pruritus on the most thickened plaques and disfiguring diffuse pigmented sequelae (Fig. 1d,e). Lichenoid reactions have potentially been associated with vaccination, notably hepatitis B and influenza vaccines.10 To date, nine cases of new-onset or flare of LP,2-7 with mild presentation, were reported after COVID-19 vaccination of which six were after Pfizer/BioNTech vaccine.2-5 Considering the reported cases and our own, four had cutaneous lesions and two had oral LP. The onset time of lesions after the vaccination varied from 5 to 14 days in new-onset LP and 1 to 10 days in relapsing LP. Our case and one from Troeltzsch et al.7 highlight that such reaction might also occur with adenovirus-based COVID-19 vaccines (ChAdOx1 and Ad26 COV2.S vaccine respectively.) Neither delayed lichenoid reaction nor common LP pathogenesis is fully understood. LP is a chronic T cell-mediated dermatosis. It is not known whether such lichenoid reactions occur from a cross-reactivity between shared epitopes on keratinocytes and viral proteins or from a non-specific stimulation of Th1 pathway in susceptible individuals after the vaccine-induced cytokine environment dysregulation; LP is not considered as a severe adverse event of vaccination. Patients may thus be re-challenged with the same vaccine. Nevertheless, our case is the second to describe a relapse after rechallenge. In the first, rechallenge with a mRNA-based vaccine induced localized lesions5; but in ours, the rechallenge with an adenovirus-based vaccine induced a very extensive relapse. Herein, we reported the first case of LP induced by ChAdOx1 nCoV-19 vaccine, confirming that LP can be induced by viral vector COVID-19 vaccination. However, these vaccine-induced skin reactions should not dissuade from vaccination to protect against a life-threatening disease at a time when a third injection of COVID-19 vaccine is recommended to prolong immunity. The patient in this manuscript has given written informed consent to the publication of her case details and photographs. None. None. Data sharing not applicable to this article, as no datasets were generated or analysed during the current study.