Herpes incognito.

Can a microscopist suspect that telltale histopathologic changes of infection by herpesvirus (varicella, zoster, or simplex) are nearby even when no diagnostic epithelial changes are present in the sections being studied? Punch-biopsy specimens from three patients are presented; in two of those cases herpesvirus infection was not even a clinical consideration. The initial histopathologic sections from these patients did not show changes of herpesvirus infection, but step sections revealed focal diagnostic changes. Atypical lymphocytes were present in each of these cases. When atypical lymphocytes are found in concert with a pattern of an inflammatory-cell infiltrate that does not conform precisely to any well-defined entity, a microscopist should consider that the findings may represent changes near infection by herpesvirus. In addition, we reviewed every case we diagnosed as herpesvirus infection over an 18-month period and found that in just over two thirds of those specimens (32 out of 45 cases), atypical lymphocytes accompanied the characteristic epithelial changes induced by herpesvirus.