Viral Exanthems

1

What is the difference between an exanthem and an enanthem?

Any skin rash that appears abruptly and affects several areas of the body simultaneously is called an exanthem, from the Greek origin “ exanthema ,” which means “ breaking out .” If the rash occurs on mucosal surfaces, it is called an enanthem.

2

Which viruses cause exanthems?

Of the hundreds of viruses that infect humans, almost all may produce an exanthem. Some viruses produce an exanthem in most infected persons. These include measles, rubella, the human herpesvirus (HHV), and parvovirus B19. A few viruses produce an exanthema in less than 1% of those infected; these include mumps, respiratory syncytial virus (RSV), and equine encephalitis.

Korman AM, Alikhan A, Kaffenberger BH. Viral exanthems: an update on laboratory testing of the adult patient. J Am Acad Dermatol . 2017;76(3):538–550.

Knöpfel N, Noguera-Morel L, Latour I, Torrelo A. Viral exanthems in children: a great imitator. Clin Dermatol . 2019;37(3):213–226.

3

Identify the six childhood exanthems and their etiologies

See Table 24.1 .

4

How do viruses cause exanthems?

In the viral exanthems studied to date, the responsible virus is found within the skin, either in keratinocytes or endothelial cells. It is believed that the virus disseminates to skin during the viremic phase of infection, and the observed exanthem is the result of the host response to the virus.

5

Which viruses cause morbilliform (measles-like) eruptions?

Measles, rubella, enteroviruses, HHV-6 and -7, Epstein-Barr virus (EBV), and cytomegalovirus (CMV) ( Fig. 24.1 ).

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