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Recurrent vesicular rash over the sacrum

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References

Diagnosis: Recurrent herpes simplex virus-2

While the presentation of herpes zoster (shingles) and herpes simplex virus (HSV) is similar—grouped vesicles on an erythematous base—recurrent shingles is rare in immunocompetent patients. Also, the herpes zoster rash is generally unilateral and is not common on the buttocks.1,2

Herpes simplex virus-1 (HSV-1) generally occurs around the mouth. Herpes simplex virus-2 (HSV-2) is generally a genital rash. (Our patient was not aware that she’d had a genital primary HSV-2 infection.) That said, non-genital recurrences in the sacral region and lower extremities occur in up to 60% of patients whose primary genital HSV-2 infection also involved non-genital sites.3

Following a genital primary infection, HSV-2 lies dormant in the sacral nerve root ganglia, which innervate both the genitals and sacrum.

HSV-2 infects an estimated 5% to 25% of adults in western nations.4 In 2012, approximately 417 million people ages 15 to 49 were living with HSV-2 worldwide, including 19 million who were newly infected.5

A dormant infection that is reactivated. Following a genital primary infection, HSV-2 lies dormant in the sacral nerve root ganglia, which innervate both the genitals and sacrum. Reactivation can thus result in recurrences anywhere over the sacral dermatome.6 The sacral area is the most common non-genital site for recurrent HSV-2.3 Reactivation of HSV-2 is more common and more severe in patients with human immunodeficiency virus infection.7

Neurologic complications in some patients with genital herpes (eg, sacral radiculopathy, hyperesthesia) reinforce the hypothesis that genital herpes can infect ganglia that are also associated with sacral nerves.8 Contrary to popular belief, sacral HSV-2 is not commonly contracted from toilet seats.

How to differentiate herpes simplex from herpes zoster

As noted earlier, the location of the vesicles and unilateral nature of herpes zoster are useful in differentiating HSV from herpes zoster.

Tzanck preparation can’t be used to differentiate HSV and herpes zoster because it will demonstrate multinucleated giant cells in both cases. When necessary, viral culture can be used to distinguish the 2 conditions, although HSV often takes 24 to 72 hours to grow and herpes zoster may take up to 2 weeks.9,10 Increasingly, polymerase chain reaction is being used for this purpose.

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