The incidence of
coronavirus disease 2019 (COVID-19)-related
skin manifestations has progressively grown, in parallel with the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreading. The available evidence indicates that cutaneous signs are heterogeneous and can be divided as follows: a) erythematous rashes, b) lesions of vascular origin, c) vesicular rashes, d) urticarial rashes, and e)
acute generalized exanthematous pustulosis (AGEP),
erythema multiforme (EM) and other polymorphic/atypical reactions. Most cutaneous manifestations appear simultaneously or after respiratory and/or systemic symptoms such as
fever, even if rarely
urticaria has been reported as the first sign of the disease. It has been proposed that erythematous and vesicular rashes, as well as
urticaria, are the result of immunological activation against Sars-CoV-2, similarly to other viral exanthems; alternatively, reactivation or
co-infection of herpesviruses and
drug hypersensitivity represent possible etiologic diagnosis that has to be considered. Regarding lesions of vascular origin, ischemic ones are the result of systemic
hypercoagulability established in severe
infections, whereas
chilblains seem to be linked to the
type I-interferon massively produced to halt virus replication. AGEP is triggered by drugs, whereas EM could represent a delayed immune response to the virus or a
hypersensitivity reaction to drugs elicited by the inflammatory process built to fight the
infection. A further pathogenic hypothesis is that the virus, or its particles detected in the skin (particularly in endothelium and eccrine glands), could be responsible for certain skin reactions, including
chilblains and EM. From the available data, it appears that
chilblains are correlated with younger age and less severe disease, while ischemic manifestations occur in the elderly with severe
infection. In conclusion, larger studies are needed to confirm the suggested pathogenetic mechanisms of
COVID-19-related skin reactions and to determine the potential prognostic significance of each one.