Chilblain-like acral lesions during the COVID-19 pandemic (“COVID toes”): Histologic, immunofluorescence, and immunohistochemical study of 17 cases.

Biopsies were obtained from 17 cases of chilblain-like lesions during the coronavirus disease 2019 pandemic in France and were studied by routine histologic examination, immunohistochemistry, and direct immunofluorescence. The patients had suspected but unconfirmed infection with severe acute respiratory syndrome coronavirus 2 (negative nasopharyngeal polymerase chain reaction and serologic test results).

Patients and methods

This case series study included 17 patients (11 men and 6 women; mean age 32 years; range 15-63 years) who were referred to our dermatology department in April 2020 for cutaneous, red-violaceous, edematous, rarely necrotic, chilblain-like lesions localized on the toes (n = 9), the feet (heel and sole; n = 6), and fingers (n = 2). Among these patients, 5 mentioned recent nonspecific general symptoms preceding the onset of cutaneous lesions (cough, fever, or weakness) and 6 suspected a possible contamination from a family member (although only 2 of them had had positive test results for SARS-CoV-2). No clinical or biological evidence in favor of an underlying autoimmune disease was present (basic evaluation included routine blood tests and levels of inflammatory markers, D-dimers, antinuclear antibodies, complement, cryoglobulins, and antiphospholipid antibodies). A nasopharyngeal polymerase chain reaction test for SARS-CoV-2 and serologic testing for antibodies to this virus were performed concomitantly with the skin biopsies; all these tests had negative results. Two skin biopsies were obtained from chilblain-like lesions from each of these patients. Formalin-fixed, paraffin-embedded skin specimens were studied microscopically for various epidermal and dermal changes associated with idiopathic and autoimmune-related chilblains. To characterize cells participating in the inflammation, the sections were immunolabeled for CD3, CD4, CD8 (T, T-helper, and T-suppressor/cytotoxic cells), CD20 (B cells), CD79a (plasma cells), CD30 (activated T cells), CD68 (histiomonocytic cells), and CD303/BDCA-2 (plasmacytoid dendritic cells) with an immunoperoxidase technique and diaminobenzidine as chromogen. Snap-frozen biopsies were studied by direct immunofluorescence for the presence of immunoreactants (IgA, IgG, IgM, and C3).