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‘Covid toe’ – a strange new symptom of coronavirus infection?

May 9, 2020 / Duncan Fisher
Yes, probably, but not a very worrisome one

The more experience we have with COVID-19 infection, the more we learn about it, reasonably enough.

We’re learning so much lately, and so quickly, that it’s been difficult to keep up with what’s new.

Lately, there is ‘Covid toe’, a syndrome that looks for all the world like chilblains, that’s begun appearing so often that it’s making up half of all new dermatology cases in quite a number of clinics. The first news of this strange development arrived only a couple weeks ago, in a raft of papers out of Spain, published in the International Journal of Dermatology, the British Journal of Dermatology, and elsewhere. In the last few days Covid toe has been making its way into the popular press, too.

Is this all an epidemic of chilblains, or is it something else? Chilblains are a cold-induced vascular disorder, sometimes spoken of as ‘pernio’, or ‘perniosis’, that typically presents as red and swollen toes, that hurt. It’s a winter thing, generally. This not being the time of year that doctors expect chilblains, especially in this abundance, no one thinks that’s what these cases are.

Medical opinion is that this is almost certainly a new addition to the growing list of classifiable skin manifestations of coronavirus.

Is that known for sure? Testing for SARS-COV-2 antibodies across the presenting population is incomplete, so we can’t know for sure at this point. But the correlation between infection rates and prevalence of this very unexpected syndrome is awfully convincing.

No one knows why pseudo-chilblains should appear with coronavirus, except that they represent an inflammatory process, and inflammation is the basic histological feature of Covid infection.

So the general concept of Covid toe is pretty believable.

This is not especially dire news. Covid toe tends to appear late in the course of the disease. (Over half the patients in the biggest of the Spanish studies reported it after they’d gotten other cutaneous symptoms already.) Covid toe arrives usually when the infection is on the wane.

It also tends to happen mostly to children and young adults. This fact, combined with the late onset, has the medical community speculating that Covid toe is actually a good thing, in its way – a sign of robust immune response. By and large, it’s been noted, these are the patients most likely to go home and recover fine.

So, what should we make of all this news about Covid toe? The consensus among medical professionals is that it’s a useful diagnostic sign. Red toes don’t mean coronavirus by themselves (and they are definitely not a criterion for self-diagnosis), but doctors are being advised that patients who have summer chilblains in the middle of the present pandemic ought to be investigated for possible infection.

Is Covid toe dangerous by itself? No, not as far as has been reported.

But red and sore toes this summer are still something worth showing to your doctor.

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