Not only toes and fingers: COVID vaccine-induced chilblain-like lesions of the knees.

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The authors have no financial obligations or conflict of interest to declare.

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Dear Editor,

During the pandemic caused by SARS‐Cov‐2 infection, acral chilblain‐like lesions (CLL) have been commonly reported cutaneous manifestations of the disease even if their association with the infection has been discussed. ,

To control the diffusion of SARS‐CoV‐2 infection, a vaccination campaign is spreading around the world since December 2020; subsequently, several different cutaneous manifestations related to vaccines have been described.

Here, we describe a 52‐year‐old woman presenting with purpuric lesions on the knees and lower third of her thighs (Fig. 1a,b). History revealed that the patient underwent the injection of the first dose of ©Moderna mRNA‐1273 vaccine on August 2021 and that the lesions had appeared about 7–10 days later. Lesions presented a cold surface and did not show any changes based on temperature. A slight itching sensation and painful walking were referred by the patient, who had never had similar lesions previously in her life. Dermoscopy showed a combination of linear vessels arranged in network fashion with multiple areas of coppery clods, the latter analogously observed in CLL of the toes (Fig. 1c). Patient was given topical steroids and oral cinnarizine (due to its vasodilator potential) for 2 weeks, and a slow improvement of the lesions was seen with also a fine ending desquamation of the purpuric lesions. Numerous skin manifestations associated with the virus have been largely discussed, as well as the cutaneous reactions to vaccines. The latter mostly included pain and swelling on the injection site and localized or diffuse erythematous or urticarial rash, usually associated with an itching sensation. All these lesions were usually transitory with a spontaneous resolution and not associated with systemic symptoms, except for rare cases of angio‐oedema and laryngospasm (usually in patients with a well‐noted allergic background). Purpuric lesions after vaccination were reported almost exclusively in association with ©Pfizer BNT162b2 mRNA vaccine, and included lesions on the eyelids, systemic purpuric rashes and cases of Henoch–Schonlein purpura. , , In our case, the primary lesions both clinically and dermoscopically were very similar to the previously reported cases of CLL after Pfizer vaccination , or SARS‐Cov‐2 infection which were, however, located on the hands and feet respectively. We report this particular and unusual localization of pernio‐like lesions on the knees, to point out that the appearance of these type of lesions after COVID‐19 vaccine cannot be considered a coincidence, also because all the patients reported in the literature had never suffered of similar lesions before facing COVID‐19 or its vaccine.

Figure 1

Pernio‐like lesions bilaterally located on the knees and lower part of the thighs (a–b), dermoscopy examination with the typical coppery background associated with dotted vessels (c).

The possible pathogenic mechanisms behind the association between COVID‐19 or SARS‐Cov‐2 vaccines and purpuric or CLL lesions are unclear. Currently, the most plausible hypothesis is that Covid‐19 related CLL may represent a virus‐induced interferonopaty associated with a strong activation of innate immune system and fast clearance of the virus and antibodies.

The appearance of purpuric and/or CLL lesions after administration of different SARS‐Cov‐2 vaccines seems to suggest however that these lesions could be also considered as a particular form of exanthema induced by the activation of the immune system against the viral spike protein irrespectively of its natural o synthetic origin in predisposed individuals.