Time of Onset of Selected Skin Lesions Associated with COVID-19: A Systematic Review.

Introduction: Distinct skin lesions associated with coronavirus disease 2019 (COVID-19) have been described, but data regarding their time of onset during the COVID-19 course are scant. Our objective was to systematically review the studies reporting the time of onset of selected skin lesions with respect to the reported onset of the COVID-19 core symptoms.
Methods: A comprehensive search of studies published before 21 January 2021 was performed on MEDLINE via PubMed database using a predefined strategy to identify relevant articles.
Results: Out of 354 references, 87 were selected, reporting a total of 895 patients with skin lesions associated with COVID-19. The most frequent pattern was exanthema (n = 430, 48%), followed by vascular (n = 299, 33%), urticarial (n = 105, 12%) and others (n = 66, 7%). Skin lesions occurred more frequently in the first 4 weeks from the COVID-19 onset (n = 831, 92%), whereas prodromal or late lesions were rarer (n = 69, 8%). The urticarial and exanthema patterns were more frequent in the first 2 weeks. About the vascular pattern some differences were noted among its subtypes. Livedoid lesions occurred mainly in the first 2 weeks, while chilblain-like lesions between weeks 2 and 4. Purpuric/petechial lesions were equally distributed during the first 4 weeks. Several skin manifestations did not fall into the pattern classification, including erythema multiforme, generalized pruritus, Kawasaki disease and others.
Conclusion: The diversity in the time of onset of skin lesions as well as their polymorphic nature likely reflects the diversity of the pathogenetic underlying mechanisms.
Prospero Database Registration Number: CRD42021236331.