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. 2022 May 1;32(3):377-383.
doi: 10.1684/ejd.2022.4260.

Chilblains observed during the COVID-19 pandemic cannot be distinguished from classic, cold-related chilblains

Axel De Greef  1 , Mathilde Choteau  2 , Anne Herman  1   3 , Caroline Bouzin  4 , Liliane Marot  1   5 , Claire Dachelet  5 , Julie Lelotte  5 , Delphine Hoton  5 , Laure Dumoutier  2 , Marie Baeck  1   3
Affiliations

Chilblains observed during the COVID-19 pandemic cannot be distinguished from classic, cold-related chilblains

Axel De Greef et al. Eur J Dermatol. .

Abstract

Background: Type 1 interferon (IFN-I) response induced by SARS-CoV-2 has been hypothesized to explain the association between chilblain lesions (CL) and SARS-CoV-2 infection.

Objective: To explore direct cytopathogenicity of SARS-CoV-2 in CL and to focus on IFN-I expression in patients with chilblains.

Materials & methods: A monocentric cohort of 43 patients presenting with CL from April 2020 to May 2021 were included. During this period, all CL were, a priori, considered to be SARS-CoV-2-related. RT-qPCR on nasopharyngeal swabs and measurements of anti-SARS-CoV-2 antibodies were performed. Anti-SARS-CoV-2 immunostainings as well as SARS-CoV-2 RT-qPCR were performed on biopsy specimens of CL and controls. Expression of MX1 and IRF7 was analysed on patients’ biopsy specimens and/or PBMC and compared with controls and/or chilblains observed before the pandemic. Serum IFN-α was also measured.

Results: RT-qPCR was negative in all patients and serological tests were positive in 11 patients. Immunostaining targeting viral proteins confirmed the lack of specificity. SARS-CoV-2 RNA remained undetected in all CL specimens. MX1 immunostaining was positive in CL and in pre-pandemic chilblains compared to controls. MX1 and IRF7 expression was significantly increased in CL specimens but not in PBMC. Serum IFN-α was undetected in CL patients.

Conclusion: CL observed during the pandemic do not appear to be directly related to SARS-CoV-2 infection, either based on viral cytopathogenicity or high IFN-I response induced by the virus.

Keywords: Chilblains; COVID toes; COVID-19; immunostaining; SARS-CoV-2; Type 1 interferon.

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