3.2 Drug induced maculopapular exanthema
In general, about 7% of hospitalized patients develop drug
hypersensitivity reactions of variable severity, and exanthema occurs in
2-3% of these cases (70, 71 ).
Both, drugs and metabolites of drugs might elicit exanthematous
drug-hypersensitivity reactions (Table 4).
Some skin lesions observed in COVID-19 patients might result from
cutaneous type IV (T-cell mediated) drug hypersensitivity reactions.
Typical immunologic characteristics of maculopapular eruptions are
summarized in Figure 5B (type IVb) and 5C (type IVc) and histologic
features are summarized in Table 5 and shown in Figure 6B. The most
common histologic feature of drug-induced maculopapular exanthema is a
perivascular dermal lymphohistiocytic infiltrate with or without
infiltration of eosinophilic granulocytes. The epidermis can be normal
or exhibit interface changes with vacuolar degeneration of the basal
layer, apoptotic keratinocytes and exocytosis of lymphocytes can be
present. Additional features can be edema in the upper dermis,
extravasation of red blood cells and dilatation of blood vessels. It is
often impossible to histologically distinguish viral and drug induced
exanthema. Lichenoid – and less frequently- spongiotic or psoriasiform
pattern of reactions may be related to maculopapular drug reactions.
Sometimes even systemic eosinophilia and elevated CRP levels might occur
(72 ). Typical immunologic characteristics of maculopapular
eruptions are summarized in Figure 5B (type IVb) and 5C (type IVc) and
histologic features are summarized in Table 5 and shown on Figure 6B.