What we have discovered about the "chilblains" caused by Covid-19

The results come from a study conducted on patients who showed, along with Covid-19, skin lesions similar to seasonal chilblains. At the base there would be the typical mechanisms of inflammatory and autoimmune reactions

Photo: andreas160578 | Pixabay From the lungs to the tips of the hands and feet: Since the first cases of 2020, Covid-19 has also been associated with manifestations of skin lesions. Among these, very frequent are those at the extremities of the body, completely similar to cold chilblains (also called seasonal chilblains), widespread especially among children and young people. The actual link between Sars-Cov-2 infection and the formation of chilblains has not yet been demonstrated, but now a study conducted by researchers from the Hôpital Saint Louis in Paris adds a new piece to the information already known. According to the researchers, in fact, the biological mechanisms underlying the “Covid chilblains” are the same as the seasonal ones, and seem to involve an immune response with high levels of autoantibodies and interferon, a key molecule involved in antiviral responses. The results of the study were published in the British Journal of Dermatology.

Identikit of Covid-19 chilblains

Chilblains are inflammatory skin growths that mainly involve the fingers and toes and which are thought to be triggered by the cold. Since the cause is unknown for most of them, they are called seasonal chilblains, but these lesions can also be associated with autoimmune diseases such as lupus erythematosus or vasculopathies (inflammatory diseases of the blood vessels).

As reported by a study published last July in the Journal of Investigative Dermatology, already in March 2020, a few weeks after the start of the spread of Covid-19 in Italy, numerous reports of skin lesions had been recorded tips of hands and feet quite similar to seasonal chilblains.

Over the following months, then, various studies have independently observed a spatial and temporal association between skin lesions of this type and Sars-Cov-2 infections in many countries around the world, including Italy, Spain, Germany, the United Kingdom, France and the United States. The cases indicated by the reports were all very similar to each other: cold, swollen and painful extremities of the body followed by the pink-purple skin color and, finally, the appearance of blisters and actual skin lesions. Furthermore, the patients presenting with these symptoms were mostly young (the average age of cases was 25 years) and many had had close contact with individuals with Covid-19, although almost all did not report the typical respiratory symptoms of the infection. coronavirus.

The study

Despite the numerous reports and the possible correlation with Sars-cov-2 infection, the pathophysiology of these lesions has not been adequately investigated, and remains unclear . This is why the Paris researchers wanted to study the differences in the activation of the immune system of the skin and blood of individuals with this particular clinical manifestation compared to healthy people and those with classic seasonal chilblains. The study included 50 participants who had "Covid chilblains" on their toes and 13 with similar chilblains lesions, but which arose before the pandemic.

Scientists analyzed inflammatory markers of the disease for each group. skin, blood vessels and the expression profiles of genes that are usually involved in immune responses: from their results it would seem that the mechanisms underlying both types of chilblains are extremely similar, involving both molecules typical of inflammatory responses, type interferons. I, some autoantibodies (antibodies mistakenly directed against the tissues of the organism to which they belong, at the base of many autoimmune diseases) and molecules involved in the dysfunctions of the blood vessels caused by inflammations and autoimmune diseases.

"Epidemiology and the clinical features of frost-like lesions have been extensively studied and published, however, little is known on the pathophysiology involved. Our study provides new insight into this, "said senior author of the study, Charles Cassius. The researchers also advanced a hypothesis on the possible explanation behind the findings: Sars-cov-2 infection would strongly trigger the expression of genes stimulated by type I interferon, which help in antiviral protection (and which are activated not only in all antiviral responses, but also in autoimmune and inflammatory diseases). of the chilblains. It should be emphasized that in 2021 the reports due to chilblains from Covid-19 decreased significantly compared to what was recorded at the beginning of the pandemic, but continuing to study these mechanisms could help shed light on the pathophysiology of Sars-cov infection. -2 in the round.


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