Frostbite: Scientist found out Why Coronavirus causes it

Frostbite appears with a sign that you have red or purplish fingers from the cold. These skin damage had been observed at the start of the epidemic as a symptom of Covid-19. A study reveals the extent to which this symptom occurs.

Last April, dermatologists had indeed alerted to these skin lesions associated with the coronavirus. While knowledge on the subject was limited, Catherine Olivieres-Ghouti, member of the Union of Dermatologists-Venereologists (SNDV), still felt that these frostbite “were not a sign of seriousness”.

Sign of “Effective Immunity”
According to a study by researchers at the Nice University Hospital of 40 patients, these lesions signify the body’s “particularly effective” innate immunity to pathogens.

Of the 40 patients studied who suffered from frostbite, all PCR tests were negative, and only a third of them tested positive. This, while they had all been in contact with or suspected of being infected with Covid-19 during the previous three weeks.

To confirm these first results, the researchers measured and compared in vitro the activity of innate immunity cells between three types of patients: those who presented with frostbite, those who suffered from non-severe forms of the coronavirus of patients get Hospitalized. Thus, it turned out that “the former’s cells have much higher levels of IFN? expression than those of the other two groups. The rates calcualted in the cells of hospitalized patients with severe forms of Covid-19 are even meagre “, explains Professor Thierry Passeron, who led the study.

As the world is in a fix with the second wave of the pandemic, the dermatologist again notes the increase in frostbite cases. “We must nevertheless reassure those who suffer from it: even if they are painful, these attacks are not severe and regress without sequelae. They sign an infectious episode with SARS-CoV-2 which has already ended in the majority of cases. . The affected patients eliminated the virus efficiently and quickly after their infection,” he said.

Thus, if the severe forms of Covid-19 seem to be linked to a defect in adaptive immunity, making it impossible to produce sufficient cells and antibodies specific for SARS-CoV -2, frostbite could be at the other end of the spectrum, and illustrate an overreaction of innate immunity.

During the first epidemic peak which began in March, some dermatologists noted an unusual increase in consultations linked to frostbite. A new study provides a clue to understanding the link between this symptom and the coronavirus.

Loss of taste and smell, and new frostbite repoted: the coronavirus continues to pressurize specialists with unusual symptoms. During the first lockdown, several people worried about frostbite’s appearance on their fingertips, but especially their feet. The national union of dermatologists and venereologists (SNDV) had even alerted on the subject in early April. It explains that “these manifestations can be associated (with the coronavirus)”.

Since then, the link between frostbite and Covid-19 has become more transparent. They are linked to an immune reaction “too strong” to the infection, according to a research team from Nice who recently published a study on the subject. An unpleasant symptom, but rather reassuring: a person with frostbite has never developed a severe form of the disease, say specialists. Marianne explains everything to you.

“It was the city dermatologists who noticed all these cases first”, explains Dr Catherine Oliveres-Ghouti, dermatologist and member of the SNDV board. Quickly, the profession’s union brought together 700 specialists on Whatsapp conversations and brought up many similar cases. “This alerted us: frostbite is usually linked to the cold, while last April, it was relatively mild,” continues the specialist. “In other words, at the following time of year, on the Côte d’Azur, it is surprising,” adds Professor Passeron, a dermatologist at the CHU de Nice. However, most of these patients are at least suspected of having been in contact with people infected with the coronavirus, even if their PCR tests are negative. Even more, members of the same family have the same symptom – which is hardly ever the frostbite case.

This is what led Professor Passeron’s team to take a closer look at this manifestation of Covid-19. Between April 9 and April 17, the team studied all the people presented to the Covid cell with this type of frostbite or about 40 patients. “None of these people had a severe form. Above all, they were all young. With one exception, all were between 15 and 25 years old”, explains the dermatologist. This is one of the highlights: the patients concerned are all young and present only mild, or even asymptomatic, forms of the disease. “We have never seen this symptom in people hospitalized with respiratory problems. It is not the first signs of a serious form”, adds Dr Oliveres-Ghouti. This manifestation is precisely linked to a great reaction of the immune system.

When the virus enters our body, the first line of defence sets in innate immunity. It takes place when a virus arrives with which we have never been in contact. In the case of Covid-19, this innate immunity, therefore, seems in part to result in frostbite. This would mean that the body has defended itself well against the infection, if not too much. A kind of collateral damage linked to an overreaction of the immune system. This explains why the people concerned are so young: the response to viral infection is often more effective in this part of the population.

So why are the PCR tests of those affected negative? Frostbite usually appears three weeks after contact with the virus, so it is no longer detectable with a trial. This is indeed a late reaction to infection. What about serological tests, which detect antibodies’ presence, which is also negative in the patients concerned? After this first line of defence and immune reaction specific to each infection occurs, this involves the production of antibodies. “However, we know that patients with mild or asymptomatic forms rarely develop antibodies,” explains Professor Passeron.