Viral exanthems

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Chapter 24 Viral exanthems

William L. Weston, MD

1. What is the difference between an exanthem and an enanthem?

Any skin rash associated with a viral infection is called an exanthem. 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 herpes viruses, and parvovirus B19. A few viruses produce an exanthema in less than 1% of those infected; these include mumps, respiratory syncytial, and equine encephalitis.

Scott LA, Stone M: Viral exanthems, Dermatol Online J 9:4, 2003.

Weston WL, Lane AT, Morelli JG: Viral infections. In Weston WL, Lane AT, Morelli JG, editors: Color textbook of pediatric dermatology, 4th ed, St Louis, 2007, Mosby, pp 113–138.

3. 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.

4. Which viruses cause morbilliform (measles-like) eruptions?

Measles, rubella, enteroviruses, human herpesvirus (HHV) –6 and –7, Epstein-Barr virus (EBV), and cytomegalovirus (CMV) (Fig. 24-1).

Figure 24-1. Morbilliform viral eruption. Numerous widespread red macules and papules.

(Courtesy of the Walter Reed Army Medical Center.)

Ramsay M, Reacher M, O’Flynn C, et al: Causes of morbilliform rash in a highly immunized English population, Arch Dis Child 87:202–206, 2002.

5. Which viruses cause grouped blisters on a red base?

Herpes simplex virus and varicella-zoster virus (Fig. 24-2A).

6. Which viruses cause hand, foot, and mouth disease?

Coxsackie A16, ECHO 71, and other enteroviruses cause hand, foot, and mouth syndrome (Fig. 24-2B).

Figure 24-2. A, Grouped vesicles limited to a dermatome in herpes zoster infection. B, Discrete palmar vesicle in epidemic hand, foot, and mouth syndrome.

(Panel A courtesy of James E. Fitzpatrick, MD.)

Fölster-Hoist R, Kreth HW: Viral exanthems in childhood—infectious (direct) exanthems. Part I: classic exanthems, J Dtsc Dermaol Ges 7:309–316, 2009.

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