4. Drug induced vasculitis
Drug hypersensitivity reactions with changes of the vasculature or
vascular pathways such as vasculitis, livedo racemosa or purpura
represent a proportion of 10-20% of cutaneous reactions to drugs and
can occur relatively late (7-14 days) during or even after drug
exposure, but the time of onset to the related drug varies and depending
on the causative drug (74 ).
Numerous drugs can induce vasculitis, which manifests primarily as
cutaneous vasculitis, mediated as III hypersensitivity reactions (Table
3), i.e. immune complex deposits with antigen excess in arteries,
arterioles, venules or capillaries (Fig. 8). It is of notice that some
drugs might also induce antibody production (62 ).
Drug-induced vasculitis includes leukocytoclastic or hypersensitivity
vasculitis, necrotizing vasculitis, Panarteritis-nodosa like vasculitis
and others (62 ).
Histologic features of vasculitis are an inflammatory infiltrate in the
wall of dermal or subcutaneous vessels (which can be neutrophilic,
lymphocytic or granulomatous), red blood cell extravasation, variable
fribrinoid necrosis of vessel walls and nuclear debris (74 ).
The number of drugs, which have been reported to be applied to COVID-19
patients all over the world is high and ranges from specific antiviral
drugs, antiphlogistics, antibiotics, anti-coagulants, immunosuppressive
as well as immunoregulatory drugs. All of these drugs are approved and
tested for other infectious diseases or entities so that not much
experience about putative side effects in COVID-19 patients exists and
knowledge gained about skin lesions induced by drugs applied during
other diseases can only be used and transferred to speculate on this
issue.
Summing up, COVID-19 skin manifestations, could be caused for each one
or a mixture of the components mentioned above i.e. reaction to the
infection, drug hypersensitivity reaction, pre-existing immune state of
the skin/immune system, combined with an impaired general health
condition and other co-factors such as age of the individual. Therefore,
it is important to discuss also putative additional trigger factors
related primarily to the susceptibility to infection with SARS-CoV-2 and
the risk to undergo severe courses of COVID-19 as an indirect factor
predisposing subsets of patients to skin and vascular lesions.