Chilblainlike Lesions—Chilblainlike lesions (CBLLs) account for 19% of skin manifestations associated with COVID-1913 and present as erythematous-purplish, edematous lesions that can be mildly pruritic or painful, appearing on the toes—COVID toes—and more rarely the fingers (Figure 2). They were seen epidemically during the first pandemic wave (2020 lockdown) in several countries, and clinically are very similar to, if not indistinguishable from, idiopathic chilblains, but are not necessarily associated with cold exposure. They appear in young, generally healthy patients or those with mild COVID-19 symptoms 2 to 4 weeks after symptom onset. They regress spontaneously or under local corticosteroid treatment within a few days or weeks. Histologically, CBLLs are indistinguishable from chilblains of other origins, namely idiopathic (seasonal) ones. They manifest with necrosis of epidermal keratinocytes; dermal edema that may be severe, leading to the development of subepidermal pseudobullae; a rather dense perivascular and perieccrine gland lymphocytic infiltrate; and sometimes with vascular lesions (eg, edema of endothelial cells, microthromboses of dermal capillaries and venules, fibrinoid deposits within the wall of dermal venules)(Figure 3).16-18 Most patients (>80%) with CBLLs have negative serologic or polymerase chain reaction tests for SARS-CoV-2,19 which generated a lively debate about the role of SARS-CoV-2 in the genesis of CBLLs. According to some authors, SARS-CoV-2 plays no direct role, and CBLLs would occur in young people who sit or walk barefoot on cold floors at home during confinement.20-23 Remarkably, CBLLs appeared in patients with no history of chilblains during a season that was not particularly cold, namely in France or in southern California, where their incidence was much higher compared to the same time period of prior years. Some reports have supported a direct role for the virus based on questionable observations of the virus within skin lesions (eg, sweat glands, endothelial cells) by immunohistochemistry, electron microscopy, and/or in situ hybridization.17,24,25 A more satisfactory hypothesis would involve the role of a strong innate immunity leading to elimination of the virus before the development of specific antibodies via the increased production of type 1 interferon (IFN-1); this would affect the vessels, causing CBLLs. This mechanism would be similar to the one observed in some interferonopathies (eg, Aicardi-Goutières syndrome), also characterized by IFN-1 hypersecretion and chilblains.26-29 According to this hypothesis, CBLLs should be considered a paraviral rash similar to other skin manifestations associated with COVID-19.30
FIGURE 2. Chilblainlike lesions (so-called COVID toes) manifested with red-violaceous macules over the distal toes.
Acro-ischemia—Acro-ischemia livedoid lesions account for 1% to 6% of skin manifestations and comprise lesions of livedo (either reticulated or racemosa); necrotic acral bullae; and gangrenous necrosis of the extremities, especially the toes. The livedoid lesions most often appear within 15 days of COVID-19 symptom onset, and the purpuric lesions somewhat later (2–4 weeks); they mainly affect adult patients, last about 10 days, and are the hallmark of severe infection, presumably related to microthromboses of the cutaneous capillaries (endothelial dysfunction, prothrombotic state, elevated D-dimers). Histologically, they show capillary thrombosis and dermoepidermal necrosis (Figure 4).
FIGURE 3. Histopathology of chilblainlike lesions (so-called COVID toes) shows scattered epidermal keratinocyte necroses, severe edema of the papillary dermis, and dermal lymphocytic infiltration (hematoxylin-eosin-saffron, original magnification ×100).
Other Reported Polymorphic or Atypical Rashes—Erythema multiforme–like eruptions may appear before other COVID-19 symptoms and manifest as reddish-purple, nearly symmetric, diffuse, occasionally targetoid bullous or necrotic macules. The eruptions mainly affect adults and most often are seen on the palms, elbows, knees, and sometimes the mucous membranes. The rash regresses in 1 to 3 weeks without scarring and represents a delayed cutaneous hypersensitivity reaction. Histologically, the lesions show vacuolization of basal epidermal keratinocytes, keratinocyte necrosis, dermoepidermal detachment, a variably dense dermal T-lymphocytic infiltrate, and red blood cell extravasation (Figure 5).
FIGURE 4. Acro-ischemia livedoid lesions from an elderly patient with severe COVID-19 manifested histologically with epidermal necrosis, dermal capillary thromboses and necroses, red blood cell extravasation (purpura), and a moderately dense diffuse lymphocytic infiltration (hematoxylin-eosin-saffron, original magnification ×200).
Leukocytoclastic vasculitis may be generalized or localized. It manifests clinically by petechial/purpuric maculopapules, especially on the legs, mainly in elderly patients with COVID-19. Histologically, the lesions show necrotizing changes of dermal postcapillary venules, neutrophilic perivascular inflammation, red blood cell extravasation, and occasionally vascular IgA deposits by direct immunofluorescence examination. The course usually is benign.
FIGURE 5. Erythema multiforme–like eruption following COVID-19 infection manifesting histologically with epidermal keratinocyte necroses and dermoepidermal bullae (hematoxylin-eosin-saffron, original magnification ×200).
The incidence of pityriasis rosea and of clinically similar rashes (referred to as “pityriasis rosea–like”) increased 5-fold during the COVID-19 pandemic.31,32 These dermatoses manifest with erythematous, scaly, circinate plaques, typically with an initial herald lesion followed a few days later by smaller erythematous macules. Histologically, the lesions comprise a spongiform dermatitis with intraepidermal exocytosis of red blood cells and a mild to moderate dermal lymphocytic infiltrate.
Erythrodysesthesia, or hand-foot syndrome, manifests with edematous erythema and palmoplantar desquamation accompanied by a burning sensation or pain. This syndrome is known as an adverse effect of some chemotherapies because of the associated drug toxicity and sweat gland inflammation; it was observed in 40% of 666 COVID-19–positive patients with mild to moderate pneumonitis.33
“COVID nose” is a rare cutaneous manifestation characterized by nasal pigmentation comprising multiple coalescent frecklelike macules on the tip and wings of the nose and sometimes the malar areas. These lesions predominantly appear in women aged 25 to 65 years and show on average 23 days after onset of COVID-19, which is usually mild. This pigmentation is similar to pigmentary changes after infection with chikungunya; it can be treated with depigmenting products such as azelaic acid and hydroquinone cream with sunscreen use, and it regresses in 2 to 4 months.34