Reply to 'New-onset cutaneous lichen planus triggered by COVID-19 vaccination' by Merhy et al.

Abstract

We have read with great interest the article recently published by Merhy et al.1 who reported a case of de-novo lichen planus occurring after Pfizer-BioNTech COVID-19 vaccine. We, herein, describe an analogous case that was referred at the Dermatology Unit of the University Hospital Federico II, Naples, in November 2021. A 59-year-old man presented with a widespread pruritic rash occurring 2 weeks after the first dose of Pfizer-BioNTech COVID-19 vaccine. Medical history was positive for arterial hypertension, diabetes and previous osteosarcoma of the right humerus (surgically removed about 30 years ago, followed by chemotherapy and currently in oncological follow-up), and no new medications were introduced before the rash onset. On physical examination, there were multiple purpuric and excoriated papules along with a brown-greyish discoloration on the trunk and limbs (Fig. 1). Dermoscopic examination revealed the presence of irregular pigmentation, some spotted grey dots, regular pseudo-network and keratinic material (Fig. 2). No mucosal lesions were detected. Routine blood tests, including hepatitis B and C markers, were unremarkable. A skin biopsy revealed the presence of irregular epidermal hyperplasia, wedge-shaped hypergranulosis, and a dense lymphocytic infiltrate at the dermal–epidermal junction with few plasma cells and eosinophils in the dermis. Given the clinical and histological features along with the temporal correlation with the vaccination, a diagnosis of lichenoid reaction following COVID-19 vaccine was made. Vaccination is a well-known stimulus for lichenoid reactions as it has been reported mainly after hepatitis B vaccine, and also, although rarely, after influenza one.2-4 Time of rash onset is generally variable between few days up to three months and may present with a wide range of clinical appearances, from only mucosal, to cutaneous, linear or eruptive.2-4 Concerning hepatitis B vaccine, a molecular mimicry mechanism has been postulated as there are shared epitopes between antigenic vaccine epitopes and keratinocytes.5 By contrast, the mechanism underlying COVID-19 vaccine is still under investigation. After vaccination, several flares of a psoriasis, atopic dermatitis, lichen planus and others inflammatory chronic skin diseases have been reported.6 Nevertheless, few cases of de-novo cutaneous or oral lichen planus have been described after vaccination with messenger RNA (m-RNA)-based COVID-19 vaccines, as a result of the induced Th1 response and the consequent storm of interleukin-2, tumour necrosis factor-α and interferon-γ.1, 7, 8 Anyway, given the high number of vaccinated people against SARS-CoV-2 virus along with the very few related cases of de novo o reactivating lichen planus reported in literature, COVID-19 vaccination should not be discouraged, although physicians should be aware of the possible occurrence or worsening of some chronic inflammatory skin diseases. The patient in this manuscript has given written informed consent to publication of its case details. None declared. Elisa Camela: conceptualization, validation, visualization, writing – original draft preparation, writing – review and editing. Gianluca Guerrasio: data curation, formal analysis, investigation, visualization, writing – original draft preparation. Cataldo Patruno: data curation, investigation, methodology, visualization, writing – original draft preparation. Massimiliano Scalvenzi: data curation, investigation, methodology, visualization, writing – original draft preparation. Nicola Di Caprio: data curation, investigation, methodology, visualization, writing – original draft preparation. Gabriella Fabbrocini: data curation, validation, visualization, writing – original draft preparation. Maddalena Napolitano: conceptualization, validation, visualization, writing - review and editing, supervision. All authors read and approved the final version of the manuscript. None. The data are reported in the current study.