COVID toes may be a sign on bodies the virus couldn’t infect

It looks like the worst of the pandemic is behind us, but the most mysterious symptom of the virus — “COVID toes” — still has experts scratching their heads.

In the earliest months of the pandemic, doctors began to note that patients often suffered from purple, red, swollen toes. Some even experienced blistering on their toes and extreme pain.

“At its most mild, people complain of it being like a mild itch,” says Esther Freeman, a dermatologist and epidemiologist at Harvard Medical School. “At its most severe, it’s so painful that some patients can’t put their shoes on for a couple of weeks.”

The condition became so common that some physicians, who once saw only one to two patients per year with these types of symptoms (also known as chilblains) were suddenly seeing dozens in a month.

And experts were mystified…

While many viruses can cause rashes and other areas of the body, chilblains due to an infection has always been considered rare, so much so that Freeman says, “If you had asked, say, 100 dermatologists before the pandemic what rashes would you expect to see with a virus, pernio chilblains would not have made the list — it would not have made the top 50.”

So what really is behind the phenomenon of COVID toes?

What the experts are finding as they learn more

You may find this hard to believe, but a debate has arisen as to whether a COVID infection is even the cause of these discolored, painful toes.

That’s because numerous patients who presented with the swollen digits never developed other symptoms of COVID — and many even tested negative using a PCR test.

In fact, research out of Northern California showed that just 17 of 456 patients suffering from COVID toes tested positive for the virus via PCR. And only a single person out of a sampling of 97 tested positive for COVID antibodies.

Yet, a landmark study published in the British Journal of Dermatology, which analyzed the blood and skin samples of 50 patients who tested negative on PCR — yet suffered from chilblain — made two important findings that may explain it all:

1. Compared to healthy patients, those suffering from COVID toes also showed high levels of autoantibodies (immune proteins in the blood that attack the body’s own tissues)
2. COVID toes patients also had elevated levels of proteins, known as type I interferons, which serve as the first line of defense against viral infections

According to COVID experts, this suggests that an overly aggressive immune response to the virus is likely behind the symptoms.

“The way I explained it to my patients is COVID toes are almost too much of a good thing,” Freeman says. “Your body did a pretty good job of fighting off the virus, and in fact it had a pretty appropriate immune response in that there was a lot of this interferon around. And a side effect of having all this interferon around is that your toes turn purple.”

These same high levels of interferon production could be why so many patients test negative to the virus, since scientists say the interferon helps clear the infection prior to antibodies forming.

Sources:

Mysterious wave of COVID toes still has scientists stumped – National Geographic

The regulation of inflammation by interferons and their STATs – NIH