COVID-19: Which symptoms show on the skin, and why bats do not fall ill

Infections with SARS-CoV2 also manifest themselves on the skin. Different patterns of dermatological symptoms were presented and the underlying pathophysiology discussed at the virtual EADV Congress 2020.

Infections with SARS-CoV2 also manifest themselves on the skin. Different patterns of dermatological symptoms were presented and the underlying pathophysiology discussed at the virtual EADV Congress on 29 October 2020.

Infections with SARS-CoV2 manifest themselves in various organs, including the skin. In order to better classify these skin diseases, Spanish dermatologists collected images and clinical data of skin diseases in COVID-19 patients and found some five predominant hypothetical patterns. According to Cristina Galván (Hospital Universitario de Móstoles, Madrid), these are pseudo-chilblains, vesicular eruptions, wheals, maculopapular rashes, and livedo, or necrosis.

Pseudo-chilblains in almost 20% of patients

According to previous observations, the most frequent symptom on the skin was pseudo-chilblains, which appeared in erythematous swellings with vesicular eruption and pustules on hands and feet in about 19% of patients. Accompanying symptoms were pain (32%) and skin itching (30%). These pseudo-chilblains occurred mainly in younger patients and usually develop late in the course of the disease. They are usually associated with a good general prognosis.

Pseudo-chilblains have been observed in COVID-19 patients in many countries, but serological or virological parameters were usually negative. So far, according to Galván, there is no evidence of a causal relationship between SARS-CoV2 infection and these pseudo-chilblains.

Livedo and necrosis associated with poor prognosis

Livedo or necrosis, which were observed in about 6% of patients, were associated with a poor prognosis (10% mortality). Ischaemia of the trunk and acral ischemia, which are clinically equivalent to occlusive vascular disease, occurred predominantly in older people.

Cytokine storm triggered by a cGAS/STING pathway

Little is known about the pathophysiology of these skin diseases associated with COVID-19, according to Michel Gilliet (Department of Dermatology, University Hospital of Lausanne, Switzerland). Skin samples showed severe vascular damage, but the Swiss working group was unable to detect viruses in the skin.

The working group suspects that the cell damage mediated by SARS-CoV2 promotes pathological changes in the skin. Large amounts of self DNA are released from the dead cells, which is taken up by macrophages. It activates the cGAS/STING metabolic pathway, which in turn leads to the release of inflammatory cytokines and interferons (IFNs).

Gilliet suspects that this is not only a mechanism in the skin, but that this pathway is for example, also involved in triggering the cytokine storm in the lungs.

Evidence to support this model is found in studies of bats. Their ability to activate STING is reduced. Due to their high flight activity, the body temperature of bats rises sharply, causing many cells to die. To prevent the resulting inflammation, the STING activation is switched off in bats. This also allows the animals to be a reservoir for SARS-CoV2 without becoming ill.

Source:
Symposium "SARS-CoV-2". 29th Congress EADV Virtual, 29 to 31 October 2020, Session ID D2T02.4.

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