COVID-19 is associated with a wide range of skin signs.
The following six main clinical patterns have been proposed for such manifestations most recently: (i) urticarial rash, (ii) confluent erythematous/maculopapular/morbilliform rash, (iii) papulovesicular exanthem, (iv) chilblain-like acral pattern, (v) livedo reticularis/racemosa-like pattern, and (vi) purpuric "vasculitic" pattern. Livedo or necrosis - blotchy red or blue appearance with a net-like pattern - was associated with increased disease severity while measles-like (morbilliform) rash was generally seen in patients with moderate to severe infection (like in the patient shown on the left who died) and pseudo-chilblains, a late sign of COVID-19, was associated with decreased severity and more likely to happen for younger patients. The median duration of chiblain-like acral pattern, however, was significantly longer that all other patterns. One study of 200 patients found the following frequencies of these signs: 10.2% for Urticarial rash; 25.7% for confluent erythematous/maculo-papular/morbilliform rash; 15.5% for papulovesicular exanthem, 24.6% for a chilblain-like acral pattern; 2.1% for a livedo reticularis/racemosa-like pattern; and 6.9% for a purpuric vasculitic pattern. 15% of skin patterns were not clearly classified while 6.5% had more than one pattern present.
The prevalence of cutaneous involvement was 7.8% in a binational Chinese-Italian cohort of 678 hospitalized adults with laboratory-confirmed disease. Dermatologic reactions after COVID-19 vaccines have been also reported and can mimic SARS-CoV-2 infection itself (eg, pernio/chilblains). The prevalence was the highest after the 2nd dose of mRNA-1273 (over 12% in Moderna), although only 1-2% experienced it with ChAdOx1 nCov-19 vaccine (AstraZeneca).
Delayed large local reactions were most common among vaccinees, followed by local injection site reactions, urticarial eruptions, and morbilliform eruptions. In a study of 414 people, forty-three percent of patients with first-dose reactions experienced second-dose recurrence. Additional less-common reactions included pernio/chilblains, dyshidrotic eczema, psoriasiform dermatitis, cosmetic filler reactions, zoster, herpes simplex flares, and pityriasis rosea-like reactions.
Some of more serious reactions could be exacerbation of Erythema multiforme. It mostly happens in mild form of a sudden rash that goes away in a few weeks but could progress to larger raised patches that look like a target or "bulls-eye" and may have a blister or crust. Relapses of autoimmune bullous disease have been also reported
as well as new onset Lichen planus, immune complex vasculitis or flares of subacute cutaneous lupus erythematosus, psoriasis and atopic dermatitis.
Morphologic misclassification is, however, possible.
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