Paraviral eruptions in the era of COVID-19: Do some skin manifestations point to a natural resistance to SARS-CoV-2?

Abstract

Paraviral eruptions, such as the papular-purpuric gloves and socks syndrome or eruptive pseudoangiomatosis, share the following features that distinguish them from a classic viral eruption: they are highly recognizable; the eruption usually lasts a few weeks; many different viruses and sometimes other agents can trigger them; on microscopic examination, there is no specific cytopathogenic viral effect. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can induce both a classic viral eruption and a paraviral eruption, the meaning of which in terms of pathophysiology and prognosis is very different. Some patients infected with coronavirus disease 2019 (COVID-19) have a papulovesicular eruption involving mainly the trunk. Those patients have active viremia, and some have developed pneumonia and died. Biopsy of the eruption revealed cytopathogenic viral effect, and thus there is a direct interaction of the virus with the skin; it is, therefore, a classic viral exanthema. Others, mainly young patients, developed chilblains of the fingers and toes 3 or 4 weeks after minor signs of COVID-19 or after contact with a diseased person. They did not develop severe COVID-19. Biopsy revealed classic findings of chilblains without cytopathogenic viral effect. Most of those patients did not develop specific antibodies. Those chilblains can be considered as paraviral. Classic viral manifestations are the consequence of a direct interaction of the skin with the virus, whereas paraviral manifestations result from the activation of the immune system. In the case of paraviral chilblains, I hypothesize that it is the innate immune system that rejects SARS-CoV-2. Chilblains are also observed in rare monogenic disorders called type 1 interferonopathies, where antiviral innate imunity is abormally activated. This would explain why these individuals do not develop specific antibodies, because they are probably naturally resistant to SARS-CoV-2 infection via their innate immuen system.

Fig. 1

Monomorphic papulovesicular and excoriated mildly pruritic eruption in a 54-year-old man with positive severe acute respiratory syndrome coronavirus 2 nasopharyngeal swab. The eruption appeared 6 days after fever, chills, and myalgia, and the patient also developed dysgeusia.

Fig. 2

Erythematous papules on toes, which appeared 19 days after clinical manifestations of possible coronavirus disease 2019 (fever, headache, myalgia) in a 26-year-old woman. Nasopharyngeal swab and serology were negative.