Dermal hypersensitivity reaction: a PCR-confirmed pattern of herpetic dermatitis

Herpetic dermatitis due to herpes simplex virus (HSV) and varicella zoster virus (VZV) can present with similar clinical and histopathologic features. Further confounding matters, viral cytopathic changes are not always observed in biopsy specimens. Therefore, use of polymerase chain reaction (PCR) analysis can play an integral role in the definitive diagnosis of herpetic dermatitis and in the distinction of HSV-1/HSV-2 from VZV.

Forty patients with skin biopsies (2004-2011) had PCR analysis performed to detect HSV-1/2 or VZV. Patient demographics, clinical impression and histopathologic characteristics were reviewed and correlated with PCR findings.

Overall, there was complete correlation between clinical impression, histopathology and PCR results in 21 of 40 cases. In 19 cases, clinical impression and histopathology were discrepant and in 15 of these cases PCR confirmed HSV or VZV infection. We also describe 3 cases of herpetic dermatitis without viral change that histopathologically demonstrate the pattern of a dermal hypersensitivity reaction.

The results of this study suggest that routine use of PCR for definitive diagnosis of herpetic dermatitis should be considered when there is a clinical suspicion of herpes virus infection, even when there is a lack of specific histopathologic findings. Additionally, a dermal hypersensitivity reaction should be recognized as one histopathologic manifestation of herpes incognito.