Virology and Etiopathogenesis of COVID-19 with Special Reference to Cutaneous Implications

Severe Acute Respiratory Virus Corona Virus 2 (SARS-CoV-2) has got its name Corona from Latin meaning "crown." It has crown-like spikes present on the surface, which encloses the RNA, genetic material of this deadly virus. The virus attacks pneumocytes after binding with the angiotensin-converting enzyme 2 (ACE2) of the cell surface, which ultimately leads to chemotaxis followed by leukocyte infiltration, increased permeability of blood vessels and alveolar walls, and decreased surfactant in the lung leading to various symptoms. Skin provides a window to the internal changes of the body and also to mechanisms that are not readily visible. Commonly observed skin manifestations include vesicular lesions, maculopapular exanthema, urticarial eruptions, livedo or necrosis, and other forms of vasculitis, chilblain-like lesions. The skin lesions are attributed to either the virus directly affecting the skin or interferon dysregulation due to viral RNA or vascular involvement associated with alteration in coagulation or drug-induced skin manifestations. Observation of skin involvement and the vasculature due to SARS-CoV-2 illustrates the need for a precise stratification and differential diagnostic valuation so that the mechanisms of this novel virus are clearer for better management of the condition in the future. Vascular skin lesions are not seen in all the patients of COVID, but certain lesions should definitely alarm us to evaluate for coagulation abnormalities, complement levels, and skin biopsy, especially in critically ill patients. This review attempts to outline the pathogen briefly and the pathomechanism behind the development of various cutaneous manifestations.