Fast Five Quiz: Shingles

William James, MD

Disclosures

December 11, 2019

Diagnosis of herpes zoster (shingles) is primarily based on the history and physical findings—specifically, the characteristic location and appearance of the skin eruption in association with localized pain. Systemic manifestations are uncommon and are usually confined to patients in whom the immune system has been compromised by other disease processes or chemotherapy. In most patients, confirming the diagnosis via laboratory testing usually has no use, because most tests are time consuming, lack specificity, or are unavailable outside of research facilities. In selected patient populations, however, the presentation can be atypical and may require additional testing. This is particularly true in immunocompromised patients. When acute diagnostic confirmation is desired, such tests as direct fluorescent antibody testing or polymerase chain reaction (if available) are preferred.

One of the least expensive and simplest laboratory diagnostic methods for VZV and other herpesviruses is the Tzanck smear. The Tzanck smear is performed by obtaining a scraping from the base of a fresh vesicular lesion after it has been unroofed, spreading and drying the collected material on a glass slide, staining the result with Giemsa, and examining the material with a microscope for the characteristic presence of multinucleated giant cells. The Tzanck smear confirms that the lesion is herpetic but cannot differentiate between VZV and other herpesviruses. Furthermore, this test has a limited sensitivity compared with other diagnostic methods, such as polymerase chain reaction assay. Therefore, a negative result does not rule out a herpes virus infection and should not preclude empirical treatment in patients.

No imaging tests are indicated in typical cases of cutaneous herpes zoster infection. MRI may be used in cases of myelopathy or encephalopathy as a means of excluding other etiologies.

Because the diagnosis can almost always be made on clinical grounds, skin biopsy is seldom necessary; as a rule, it is reserved for cases that are difficult to diagnose (eg, atypical lesions). On rare occasions when skin biopsy is necessary, histologic findings are similar to those of herpes simplex and varicella. Ballooning degeneration and acantholysis of keratinocytes result in an intraepidermal vesicle. Multinucleated giant cells with accentuation of nuclear material at the periphery of nuclei are characteristic.

Read more about the workup of herpes zoster.

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