Original Author | Cassandra Willyard
While new research still shows that COVID-19 does not cause inflamed toes and frostbite in infected people, the debate continues.
In March 2020, just as COVID-19 cases began to climb in Boston, Massachusetts, Esther Freeman noticed a lot of patients coming in with discolored toes. Freeman, director of global health dermatology at Massachusetts General Hospital, has seen these toes before. These itchy red-purple bumps are typical of chilblains, a skin disease common in winter. But in normal times, there are only one or two patients every winter. “Suddenly, there are now 15, 20 of these patients a day,” she said. Physicians all over the world are noticing this, and it’s interesting that the surge in patients seems to be surprisingly consistent with the development of the new crown epidemic. .
The media dubbed it the “corona toe,” and when doctors tested these patients further, most of them didn’t test positive for coronavirus. This puzzled scientists and decided to find out.
Researchers have mixed opinions on whether the “corona toe” is caused by the new coronavirus infection. | Cordelia Molloy/Science Photo Library
The latest study[1], published February 25, took an immunological perspective and analyzed 21 people who developed frostbite during the first months of the pandemic in Connecticut. Although the findings do not rule out a direct association between Covid-19 infection and frostbite, for 19 of them, the authors could not find immunological evidence that they had Covid-19 infection. This result supports the view of some researchers that the “corona toe” is caused by something unrelated to the new coronavirus. For example, maybe because these people are not wearing shoes and socks at home during the lockdown, said study lead author Jeff Gehlhausen, a dermatologist and immunologist at Yale University School of Medicine.
However, the findings raise “some very interesting questions that warrant further study,” says Freeman, who was not involved in the study. For example, the study does not rule out the possibility that people exposed to the new coronavirus may be fighting the virus by means of the innate immune response–the innate immune response is the body’s first line of defense and does not It mobilizes the body to produce detectable antibodies and T cells against the new coronavirus. So the whole mystery is still unsolved, she said.
Toes have something to say
The cause of frostbite is not fully understood. “We think of chilblains as a cold climate-related injury,” said Patrick McCleskey, a dermatologist and researcher at Kaiser Permanente in California. “We always see some chilblains in the winter and then again in the summer. It’s gone.” The researchers believe that cold may restrict blood flow, causing some cells to die, triggering an inflammatory mechanism. These reddish-purple bumps on the toes (and possibly fingers, ears, or nose) can be itchy, tingling, and sometimes extremely painful.
In this latest study, most of the subjects’ “corona toes” appeared in April and May 2020, which coincided with the surge in corona cases in Connecticut. . In the study, about 1/3 of the people said they had some symptoms of new crown infection before the “new crown toe” appeared, and 1/3 of the people said they had been in contact with a confirmed or suspected infection of the new crown.
The research team used a variety of methods to find antibodies and T cells specific for SARS-CoV-2 — the body’s signal for a adaptive immune response to pathogens . It’s been months since these people developed chilblains, and if they do have the virus, their immune systems should have had enough time to respond. But the research team only found signs of infection in two people, one of whom had been diagnosed positive for COVID-19.
Many teams are looking for SARS-CoV-2 antibodies in chilblain patients, but “no one has really tested the T-cell response hypothesis,” Freeman said. “This team has done an amazing job. .” But she also pointed out that the whole study was small, so the extrapolation was not strong, and larger epidemiological studies[2,3]have found that frostbite and new crown Correlation of viruses.
Dermatologist Thierry Passeron of the University of the Côte d’Azur in France still believes that the new crown toe originated from the new crown virus. His team [4] found evidence in patients with frostbite during the epidemic that they developed a strong innate immune response. The team speculates that many people who suffered from frostbite during the pandemic cleared the virus this way, so almost none of these people produced antibodies, he said.
Puzzle Unsolved
Previous studies[5,6] used tissue biopsy and stained samples to identify viral components to test whether patients with chilblains had been infected with the new coronavirus. Gehlhausen and colleagues tried the stain and found that the stain adhered to some of their tissue samples. They then randomly tested the stain with pre-pandemic tissue samples from a period when the new coronavirus had not yet begun, and found that the stain also marked these areas. “Our study suggests that this staining may lack specificity,” Gehlhausen said.
The link between Covid-19 infection and frostbite is still inconclusive, and some researchers are starting to consider the possibility of a lockdown theory that when the pandemic first emerged, many people spent more time barefoot at home , resulting in cold sores on the toes. It’s also possible that seeing a large number of reports of the new crown toe has made more people with symptoms decide to seek medical treatment.
For Freeman, “the whole problem has not come to light.” On the one hand, she’s seen people who, unsurprisingly, develop chilblains from walking in flip-flops in a snowstorm. On the other hand, she has also seen chilblains with no other apparent cause in coronavirus-positive patients.
The debate over the issue is also starting to polarize, Gehlhausen said. But the different theories are not incompatible with each other. “It’s also possible that both of these situations exist,” he said. “I don’t support either side.”
It is also possible that this phenomenon is decreasing. “There are still new cases of chilblains, but the numbers seem to be back to where they were before,” said Yale dermatologist William Damsky, one of the authors of the paper.
All in all, it’s a scientific question worth exploring, but the answer shouldn’t affect the way dermatologists treat their patients, McCleskey said. Chilblains generally go away on their own within two to three weeks, regardless of whether the patient has been infected with COVID-19.
He said, “Honestly, I think the frostbite can be put aside.”
References
1. Gehlhausen, J. R. et al. Proc. Natl. Acad. Sci. USA 119, e2122090119 (2022).
2. Mascitti, H. et al. Eur. J. Clin. Microbiol. Infect. Dis. 40, 2243C2248 (2021).
3. Visconti, A. et al. Br. J. Dermatol. 184, 880C887 (2021).
4. Hubiche, T. et al. JAMA Dermatol. 157, 202C206 (2021).
5. Ko, C. J. et al. J. Cutan. Pathol. 48, 47C52 (2021).
6. Colmenero, I. et al. Br. J. Dermatol. 183, 729C737 (2020).
Original titled Are ‘COVID toes’ actually caused by the coronavirus? in Nature’s News section on March 6, 2022
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