What is ‘COVID toe’? Maybe a strange sign of coronavirus infection

Before the COVID-19 outbreak, Dr. Lindy Fox, a dermatologist in San Francisco, used to see four or five patients a year with chilblains — painful red or purple lesions that typically emerge on fingers or toes in the winter.

Over the past few weeks, she has seen dozens.

“All of a sudden, we are inundated with toes,” said Dr. Fox, who practices at the University of California, San Francisco. “I’ve got clinics filled with people coming in with new toe lesions. And it’s not people who had chilblains before — they’ve never had anything like this.”

It’s also not the time of year for chilblains, which are caused by inflammation in small blood vessels in reaction to cold or damp conditions. “Usually, we see it in the dead of winter,” Dr. Fox said.

Dr. Fox is not the only one deluged with cases. In Boston, Dr. Esther Freeman, director of global health dermatology at Massachusetts General Hospital, said her telemedicine clinic is also “completely full of toes. I had to add extra clinical sessions, just to take care of toe consults. People are very concerned.”

The lesions are emerging as yet another telltale symptom of infection with the new coronavirus. The most prominent signs are a dry cough and shortness of breath, but the virus has been linked to a string of unusual and diverse effects, such as mental confusion and a diminished sense of smell.

Federal health officials do not include toe lesions on the list of COVID-19 symptoms, but some dermatologists are pushing for a change, saying so-called COVID toe should be sufficient grounds for testing.

Several medical papers from Spain, Belgium and Italy described a surge in complaints about painful lesions on patients’ toes, Achilles’ heels and soles of the feet; whether the patients were infected was not always clear, because they were otherwise healthy and testing was limited.

Most cases have been reported in children, teens and young adults, and some experts say they may reflect a healthy immune response to the virus.

“The most important message to the public is not to panic — most of the patients we are seeing with these lesions are doing extremely well,” Dr. Freeman said.

“They’re having what we call a benign clinical course. They’re staying home, they’re getting better, the toe lesions are going away.”

Scientists are just beginning to study the phenomenon, but so far chilblain-like lesions appear to signal, curiously enough, a mild or even asymptomatic infection. They may also develop several weeks after the acute phase of an infection is over.

Patients who develop swollen toes and red and purple lesions should consult their primary care doctor or a dermatologist to rule out other possible causes. But, experts said, they should not run to the emergency room, where they risk being exposed to COVID-19 or exposing others if they are infected.

“The good news is that the chilblain-like lesions usually mean you’re going to be fine,” Dr. Fox said. “Usually it’s a good sign your body has seen COVID and is making a good immune reaction to it.”