PORTLAND, ORE. – while others are not, according to Lindy P. Fox, MD, professor of dermatology and director of the hospital consultation service at the University of California, San Francisco.
“We’re learning a lot about pernio because of COVID,” Dr. Fox, a member of the American Academy of Dermatology’s Ad Hoc Task Force on COVID-19, said at the annual meeting of the Pacific Dermatologic Association. “Patients with pernio tend to either have bright red or purple individual lesions or an erythromelalgia-like presentation, often waking up in the middle of the night saying ‘my feet hurt. I can’t put sheets over my feet.’ In my experience, the patients with an erythromelalgia-like presentation tend to be a lot harder to treat.”
courtesy UCSF
Dr. Lindy Fox
Establishing terminology to describe pernio-like lesions was a challenge in the early stages of the COVID-19 pandemic, Dr. Fox added, with clinicians using terms like erythema multiforme-like, coxsackie-like, or even necrotic to describe the lesions. “I don’t think pernio is truly necrotic; I think it’s really inflammatory and purpuric,” she said.
Early in the pandemic, studies suggesting a link with these cases and COVID-19 infection include a case series of 318 patients with pernio-like skin lesions who had confirmed or suspected COVID-19. Most of these patients were generally young and healthy and most had relatively mild COVID-19; 7% were laboratory-confirmed COVID-19 positive, and 6% were close contacts of patients with confirmed COVID-19. Pernio-like lesions were the only symptoms in 55% of the patients.
In another study, researchers in France evaluated the clinical, laboratory, and pathologic characteristics of 40 patients who developed chilblain-like lesions (mostly involving the toes) during the COVID-19 pandemic and were seen as outpatients in April 2020 . All were polymerase chain reaction (PCR) negative, 30% were SARS-CoV-2 serology positive, and 60% had elevated D-dimers. Histology obtained from 19 of the patients revealed lymphocytic inflammation and vascular damage, and 8 had IgA positivity.
In a retrospective analysis of seven pediatric chilblains cases during the pandemic, researchers examined the skin biopsies to evaluate histopathological features and explored the presence of SARS-CoV-2 in the tissue. All patients were PCR negative. The authors observed cytoplasmic granular positivity for SARS-CoV-2 spike protein in endothelial cells, a feature that they said showed coronavirus-like particles, consistent with SARS-CoV-2.
Not all studies in the medical literature have demonstrated an association between pernio-like/chilblains-like lesions and COVID-19, though. An analysis of 23 patients, with skin eruptions considered associated with SARS-CoV-2 infections (including 21 cases of chilblains) during the first wave of the pandemic found that the antibody and T-cell response in patients with pandemic chilblains was the same as in negative controls.
“What’s remarkably interesting about this study is that they did autopsies of samples from patients who had died prepandemic, so there was no such thing as COVID-19,” said Dr. Fox, who was not involved with the study. “They stained for viral particles in those patients, and they were positive in a subset of patients. This makes me wonder about what the significance of that staining positivity is.”
Yet another group of investigators looked at what was happening with pernio during the waves of COVID in a study of chilblains cases in children in Spain, and found a stronger association between lockdown and cold temperature, which argues against a direct association between pernio and COVID infection.
In Dr. Fox’s experience, COVID toes can recur, especially upon exposure to cold. “What taught me this in real life is a patient who I saw remotely by video,” she recalled. “It was early on in the pandemic. I could not prove he had COVID no matter how hard I tried, but I do think he had COVID toes at that time.” When he later was confirmed to have COVID, “he got pernio in the same exact location as his original suspected COVID toes.”
According to an analysis of long COVID in the skin, based on cases reported to the American Academy of Dermatology–International League of Dermatological Societies registry from April 8 to Oct. 8, 2020, pernio-like lesions lasted a median of 12 days in patients with lab-confirmed COVID-19 and a median of 15 days in those with suspected COVID-19. But almost 7% of the 103 pernio cases were long-haulers, defined as those with dermatologic signs of COVID that lasted beyond 60 days.
“There are some patients who are resistant to treatment,” Dr. Fox said. “In addition, recurrent lesions make me think that maybe all pernio is triggered by some viral cause. This causes an immunologic phenomenon that’s responding to a viral trigger you’re trying to deal with. That may be the better way to think about COVID toes.”
Different variants of COVID also appear to be changing the characteristics of dermatologic manifestations associated with infection. Results from a large retrospective analysis of nearly 350,000 users of a COVID study App in the United Kingdom found that skin lesions were more predictive of a positive test in the Delta wave, compared with the Omicron wave, while pernio-like lesions were predictive of infection in the Delta wave but not in the Omicron wave.
“And, whether you were vaccinated or unvaccinated really did not influence whether or not you were going to have a skin rash as a presenting sign of COVID, except for the burning rash, which was less in vaccinated patients,” said Dr. Fox, who was not involved with the study.
Dr. Fox reported having no relevant disclosures.