Negative SARS-CoV-2 PCR in patients with chilblain-like lesions.

We read with interest the Correspondence by Claudio Guarneri and colleagues suggesting that chilblain-like lesions could reveal asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Several reports of cutaneous manifestations suspected to be linked to SARS-CoV-2 infection, mostly chilblain-like lesions, have been published.2, 3, 4, 5 All are case reports or retrospective case series without systematic and in-depth evaluation of cases, and in most PCR or serology testing for SARS-CoV-2 infection were not done.

We did a prospective cohort study in patients with cutaneous manifestations who were referred to Centre Hospitalier Universitaire de Nice, France, between April 9 and 17, 2020, with suspected SARS-CoV-2 infection. 40 consecutive patients (21 [53%] female) with chilblain-like lesions were included. Consistent with previous reports,2, 3, 4, 5 most patients were young, with a median age of 22 years (range 12–67; IQR 15–28). 26 (65%) patients were tested for SARS-CoV-2 RNA with RT-PCR using primers and probes recommended by WHO, and all patients were tested for SARS-CoV-2-specific IgA, IgM, and IgG antibodies with ELISAs (IgM and IgG with EDI Novel Coronavirus COVID-19 ELISA Kits [Epitope Diagnostics, San Diego, CA, USA]; and IgA and IgG with Euroimmune ELISAs [Euroimmun, Lübeck, Germany]).

25 (63%) patients were asymptomatic on physical examination, and the remaining patients had only mild symptoms compatible with COVID-19. 24 (60%) patients reported contact with a person suspected of having COVID-19. However, no patient was PCR positive at the time of consultation, a finding that is inconsistent with the PCR positivity of all three cases reported by Guarneri and colleagues. Our results are not surprising considering no patient reported having fever or signs of upper or lower respiratory tract infection in the past 3 days. However, COVID-19 serology was positive in 12 (30%) patients: seven had only IgA antibodies, three had only IgG antibodies, one had IgM and IgG antibodies, and one had IgA and IgG antibodies. This proportion is substantially higher than expected for our area (estimated at 3·4%). Although these results require further investigation, they suggest that in young patients SARS-CoV-2 is completely suppressed before a humoral immune response is induced.

Taken together, our results suggest that chilblain-like lesions are associated with mild or asymptomatic SARS-CoV-2 infection, and in this respect our findings are in accordance with the cases reported by Guarneri and colleagues. However, physicians should be aware that most patients presenting with chilblain-like lesions will probably have negative PCR results at the time of presentation.