Initially suspected to be a symptom of the virus, these purplish frostbite have been identified on the toes of some patients. Today researchers consider them to be a sign of a natural immune reaction against Covid-19.
Covid toes were identified in April 2020 by dermatologists as one of the many symptoms of SARS-CoV-2. Terrifying at first glance, since the toes turn purple and eventually heal spontaneously and without treatment in the majority of cases. Many researchers are on the prowl to understand all the symptoms of the virus and a new hypothesis is springing up in the research world. While an abnormal number of pseudo-frostbite in the toes and heels has been reported in a dozen countries, these mysterious swelling and frostbite could in fact be a sign of innate resistance to the coronavirus. In any case, this is what two Swiss researchers from the dermatology department at the Center hospitalier universitaire Vaudois (CHUV) are saying. The two specialists investigated the subject and the results appeared in the Swiss medical journal (RMS).
“A collateral damage of a very robust immunity”
“This unusual upsurge in pseudo-frostbite is all the more intriguing as the majority of cases do not present with symptoms of Covid-19 or PCR or positive serology, despite probable exposure to SARS-CoV-2. Current data suggests that these individuals are predisposed to induce robust innate immunity against SARS-CoV-2, making them resistant to infection ” explains Dr Ahmed Yatim at the dermatology department of the CHUV and co-author of the study. Dr Michel Gilliet and Ahmad Yatim explain that these swelling at the ends of the feet are associated with a significant secretion of type 1 interferons. Objectively this means that these proteins control the immune response and can interrupt the replication of the virus in the pathways. aerial. “On the one hand, early poor control of SARS-CoV-2 by IFN-I leads to disease progression to a severe form. On the other hand, a strong IFN-I response, of which pseudo-frostbite is the clinical manifestation, could make certain predisposed individuals resistant to infection by SARS-CoV-2. “Emphasize the researchers in the Swiss Medical Review. “Pseudo-frostbite therefore represents a collateral damage to an exceptional innate antiviral immunity”.
Natural resistance to SARS-Cov-2 in patients with pseudo-frostbite
According to the authors of the study, in more than 40% of cases, people with frostbite have had close contact with a Covid-19 patient but they are not positive when screened. Swiss researchers also report that family clusters of Covid-19 with several cases of frostbite within siblings have been reported, suggesting a genetic predisposition. “Interestingly, only family members with frostbite had a negative SARS-CoV-2 PCR and remained HIV negative,” they add.
What treatment for these frostbite?
“In the event of associated local symptoms (itching, burning sensation, pain), treatment with topical corticosteroids is effective and sufficient.“Reassure the Swiss Drs in their study. In addition, scientists want to better understand the protective mechanisms “The study of patients with pseudo-frostbite offers a unique opportunity to elucidate the genetic and molecular mechanisms underlying natural resistance to SARS-CoV-2. By identifying the correlates of innate protective immunity against SARS-CoV-2, this work could stimulate the development of new antiviral strategies ” conclude Dr Ahmad Yatim & Michel Gilliet.