TORONTO -- The list of possible COVID-19 symptoms continues to grow.
"COVID tongue," or symptoms characterized by irritations and lesions in the mouth and tongue, have been causing concern for researchers, as well as "COVID toes," which are characterized by rashes and inflammation in the toes and feet.
Last September, a study conducted in Spain involving 666 COVID-19 patients found that 78 participants developed lesions on their tongues. Most patients reported a reduction in taste sensation, but 5.3 per cent reported a burning sensation.
The study also found that 121 patients developed irritations on their palms and soles of their feet.
Dr. Douglas Fraser is a professor at Western University’s Schulich School of Medicine & Dentistry and a pediatric critical care physician at London Health Sciences Centre in London, Ont. He said that the tongue has a high concentration of ACE receptors, which are the receptors that the SARS-CoV-2 virus binds to.
"That causes the virus to be taken up into those cells. In the tongue, you have potential for a high amount of virus, which would create a localized inflammatory effect, and hence, you would start to have some of these red lesions, potentially," Fraser told CTVNews.ca in a phone interview on Monday.
In January, a tweet from British COVID-19 researcher Tim Spector gained global media attention after he began noticing more patients with tongue lesions.
"Seeing increasing numbers of Covid tongues and strange mouth ulcers. If you have a strange symptom or even just headache and fatigue stay at home!" Spector tweeted.
Fraser says that reports of COVID tongue symptoms are "relatively rare," although COVID toes tend to be more common in young people, something he's observed in his own research.
"In general, they're more common in younger people, children, teenagers, young adults, particularly the toes," said Fraser.
Another study from Spain published last July found evidence supporting a link between COVID-19 and lesions on the toes. A majority of the 375 participants in that study had tested negative for the virus through throat swabs and didn't exhibit any other symptoms, but the virus was detected in sweat glands and the walls of the skin's blood vessels.
Fraser is also the lead author of a Canadian study that was the first to describe endothelial injuries affecting critically ill COVID-19 patients. Endothelial injuries refer to injuries affecting the cells that line the blood vessels.
"(COVID-19) creates an inflammatory effect, then damages what we call the endothelial cells, which line the blood vessels. And along with that injury to the blood vessel, you're much more likely to have clotting or blood clotting," said Fraser.
This blood clotting can then result in lesions on the toes.
"When you have all this clotting going on, it can go to places where the blood vessels are very small, and like the toes and the end of the fingers and the tongue. So, you get the blood vessels are not only sick there, but you can also get little clots developing," Fraser explained. "So, some of these lesions, particularly on the toes, are related to blood vessels that are inflamed and angry and clotting."
"If the clots occur in the venous system, then you can actually get a backup of pressure to get swelling and redness."
In rare cases, children who contract COVID-19 can also be susceptible to multisystem inflammatory syndrome, or MIS-C, which causes inflammation in numerous parts of the body and resembles Kawasaki disease, another blood vessel inflammation disease.
"If you get MIS-C in kids, it's really just a blood vessel injury. They don't necessarily show up with terrible pneumonia in the lungs, but instead they'll show up with all sorts of different organs involved. And they may have COVID toes, which is from the blood vessels being angry and sick," Fraser said.
