The American Journal of dermatopathology
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Papular urticaria is the result of hypersensitivity (id-reaction) to bites from certain insects such as mosquitoes gnats, fleas, mites, and bedbugs. Papular urticaria is common in childhood and is characterized by symmetrically distributed pruritic papules and papulovesicles. Scratching causes erosions and ulcerations. ⋯ Papular urticaria with marked spongiosis and a dense inflammatory cell infiltrate cannot be reliably distinguished from arthropod bites on clinical and histopathologic grounds. The present study provides morphologic and immunohistochemical evidence that a type I hypersensitivity reaction plays a central role in the pathogenesis of papular urticaria. The putative antigen remains undetermined.
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Cutaneous herpesvirus infection is a common viral disorder manifest by epidermal and/or mucosal vesicle formation. Though it is believed that the virus most likely resides in regional sensory ganglia following primary infection and that cutaneous involvement represents reactivation of a latent infection, the histopathology of cutaneous nerves in sites of disease has not been well characterized. In order to assess and characterize the pathologic changes of these nerves, we retrospectively examined 54 cases of cutaneous and mucosal herpesvirus infection as defined by the presence of diagnostic multinucleate epithelial giant cells that demonstrated viral cytopathic effect. ⋯ Immunoperoxidase staining using a polyvalent antibody to human herpesvirus was performed in two cases and demonstrated viral antigen within nerve twigs. This pattern of peripheral nerve twig inflammation, along with the occurrence of more distant neural involvement, may prove to have diagnostic implications and serve as a clue in the recognition of cutaneous herpesvirus infection, particularly in cases with subtle or absent epidermal alteration. Furthermore, the presence of inflammation within and around nerves as well as degenerative changes suggest that nerve twigs are not passive conduits for viral spread but may be directly involved in infection.