Methods
Since it is quite difficult to verify, in which context the skin lesions
occur in terms of SARS-CoV-2 infections, we would like to summarize in
the next few sections current knowledge about the pathophysiologic
background of virus-induced and drug-induced lesions of the skin and the
vascular system.
Data for this Review were identified by searches of MEDLINE, Current
Contents, PubMed, and references from relevant articles using the search
terms “SARS-CoV-2”, “COVID-19”, “skin”, ”vascular system“, ”virus
(infection)“ and ”drug hypersensitivity reaction“. Only articles
published in English between 1995 and 2020 were included.
Possible pathogenic
mechanisms involved for skin manifestations
Viral rashes
Viral exanthema is defined as a skin rash, which is sometimes associated
with an enanthem and goes along with fever and other systemic symptoms
(51, 52 ). In this context, it is important to notice that also
the ACE2 receptor has been described to be expressed in the oral cavity
(11 ), lesions of the mucous membranes have not been reported so
far to occur very frequently together with skin lesions in SARS-CoV-2
positive cases,
In principle, skin manifestation of viral infections can derive by
- direct inoculation of the virus,
- dissemination or reactivation of the virus from another site or
- interaction of the virus with the immune system in general and related
cellular and humoral immune responses including virus-specific
lymphocytes and antibodies (51 ).
The onset of the skin lesions in relation to viremia and general
symptoms can help to understand the pathophysiologic mechanisms behind
the lesions in COVID-19 patients. In the case of skin lesions precede
general symptoms or might even be the only sign for a putative
infection, they might serve as important early indicators of the disease
or indicator for asymptomatic virus carriers. On the other hand-side,
skin symptoms, which occur quite late during infection or even after
resolution of main symptoms might indicate a lack of viral clearance and
cascades of immune responses induced by the virus .
Viremia often predates the typical COVID-19 symptoms and virus-specific
virology might be both, false negative or false positive due to
cross-reactivity to other members of the coronavirus family, but could
provide important information about acute or previous infection by the
analysis of virus-specific IgM and IgG. Nucleotide testing of tissue
specimens is highly sensitive and specific, but stability of samples and
RNA, contamination, and other issues may occur and limit information
gained, so that even part of smear taken from the mouth remain false
negative (52 ).