1.1 Virus induced maculopapular exanthema
Although skin biopsies are rarely taken from viral skin lesions, because the features observed are mostly not very specific, biopsies might be an option to differentiate viral exanthema from drug-induced exanthema in COVID-19 patients, in these cases it is essential to do the differential diagnosis and rule out the pharmacological cause.
To distinguish infectious exanthema from exanthema induced by drug-hypersensitivity reactions, histologic features and immunologic changes in the skin might help to diagnostically differentiate both entities.
Immunologic features of maculopapular virus exanthema known so far are summarized in Fig. 5A. Typical histologic features of infectious exanthema induced by viremia or dissemination of infectious agents through the blood are shown in Table 2 and Fig. 6A.