Further evidence that chilblains are a cutaneous manifestation of COVID-19 infection.

Dear Editor, A range of cutaneous conditions including chilblain‐like lesions have been reported in patients with coronavirus 2019 (COVID‐19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‐Cov‐2). Using clinical data and images, the authors of a recent nationwide Spanish survey identified five clinical patterns that were associated with different patient demographics, onset (timing) and prognosis.1 These include ‘acral areas of erythema with vesicles or pustules (i.e. pseudo‐chilblain),’ which occurred in one‐fifth (19%) of patients with COVID‐19 disease.1 Pseudo‐chilblains affected younger patients and occurred later in the course of the disease, with a mean duration of 12·7 days.1 Furthermore, pseudo‐chilblains were associated with a less severe disease course, including need for intensive care admission and mortality. The lesions were not uncommonly painful (32%) or associated with pruritus (30%).1 Against this background, our aim was to examine whether internet searches for chilblains have increased during the current COVID‐19 pandemic.

Google Trends® allows analysis of the relative popularity of search trends over time and geographical location.2 We examined the term ‘chilblains’ in the ‘health’ category to ascertain whether there were any obvious recurrent temporal search patterns worldwide and in the USA. We examined data over the past 12 months. These are freely available within the public domain and therefore ethical approval was not required.

There were clear trends (‘spikes’) in the relative popularity of searches for chilblains in early 2020 (Figure 1). Figure 1 also shows pictures of two individuals’ chilblains of different severity that were observed in patients without previous chilblains during the COVID‐19 pandemic.

Figure 1

Chilblains in 2020 during COVID‐19. Google Trends® data (5 May 2019 to 26 April 2020) for chilblains worldwide (a) and for the USA (b). Numbers on the y‐axis represent the search interest relative to the highest point for the given region and time (x‐axis), where 100 is the peak popularity for the term, and 0 indicates there is not enough data for the search term. (c, d) Examples of chilblains that occurred in early 2020 in children and adults, none of whom had a history of previous chilblain occurrence. The erythema and the vesicles and pustules may be clearly seen.

Our data show a clear relative increase in internet searches relating to chilblains in early 2020 during the COVID‐19 pandemic. There are a number of possible explanations. This could include true chilblain‐like lesions secondary to COVID‐19 infection. Another explanation is that patients have used internet‐based information to learn about chilblains following interaction with media content describing chilblain‐like lesions in patients with COVID‐19.3 Finally, temporally these are unlikely to represent recurrence of chilblains provoked by cold weather (similarly to worsening of Raynaud phenomenon in colder weather).4 For example, in the previously described Spanish study, pseudo‐chilblains occurred in a period of warm weather, and virtually all patients (70 of 71) did not have a previous history of chilblains.1 There is also a tentative emerging suggestion that children are disproportionately affected by chilblains, potentially due to more mild disease.

In conclusion, our data further suggest that chilblain‐like lesions might occur in COVID‐19 infection. Further research is needed to confirm the potential clinical utility of chilblain lesions in COVID‐19, including to facilitate disease suspicion and prognostication.