Is COVID Toes More Than One Condition?
Some of the initial reports of finger/toe cyanosis out of China were very alarming, with many patients developing skin necrosis or even gangrene. These were critically ill adults with pneumonia and blood markers of disseminated intravascular coagulation, and 5 out of 7 died. In contrast, the cases of pseudo-pernio reported in Europe, and now the US, seem to be much milder, usually occurring late in the illness or in asymptomatic young people. Do you think these are two different conditions?
I believe you have hit the nail on the head. I think it is really important that we don't confuse those two things. In the inpatient setting, we are clearly seeing patients with a prothrombotic state with associated retiform purpura. For non-dermatologists, that usually means star-like, stellate-like, or even lacy purpuric changes with potential for necrosis of the skin. In hospitalized patients, the fingers and toes are usually affected but, interestingly, also the buttocks. When these lesions are biopsied, as has been done by our colleague at Cornell, Joanna Harp, we tend to find thrombosis.
A study of endothelial cell function in patients with COVID-19, published in the Lancet, tried to determine whether viral particles could be found in endothelial cells. And the investigators did indeed find these particles. So it appears that the virus is endothelially active, and this might provide some insight into the thromboses seen in hospitalized patients. These patients can develop purple necrotic toes that may progress to gangrene. But that is completely different from what we're seeing when we say pernio-like or chilblains-like lesions.
The chilblains-like lesions come in several forms. They may be purple, red bumps, often involving the tops of the toes and sometimes the bottom of the feet. Some have been described as target-like or erythema multiforme–like. In others, there may not be individual discrete lesions but rather a redness or bluish, purplish discoloration accompanied by edema of the entire toe or several toes.
Biopsies that I am aware of have identified features consistent with an inflammatory process, all of which can be seen in a typical biopsy of pernio. You can sometimes see lymphocytes surrounding a vessel (called lymphocytic vasculitis) that may damage a vessel and cause a small clot, but the primary process is an inflammatory rather than thrombotic one. You may get a clot in a little tiny vessel secondary to inflammation, and that may lead to some blisters or little areas of necrosis. But you're not going to see digital necrosis and gangrene. I think that's an important distinction.
The patients who get the pernio-like lesions are typically children or young adults and are otherwise healthy. Half of them didn't even have COVID symptoms. If they did have COVID symptoms they were typically mild. So we think the pernio-like lesions are most often occurring in the late stage of the disease and now represent a secondary inflammatory response.
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Cite this: Dermatologic Changes With COVID-19: What We Know and Don't Know - Medscape - May 13, 2020.