Approximately 100 years ago Gibert first described the macular form of pityriasis rosea, and Bazin added a description of the circinate variety. Percival, in 1931, gave a good review of the subject.1
Much has been written concerning the etiology of pityriasis rosea. Etiologies that have been suggested are fungus infection, staphylococcal, and streptococcal infections of the tonsils with autointoxication, a toxic exanthem from a gastrointestinal tract infection, and psychogenic and neurogenic concepts. Viral etiology has been postulated, but viral cultures have been unsuccessful. Wile2 may have reproduced an aberrant form of the disease by experimental transmission. The most widely accepted etiology is that of a weakly infectious disease, probably of viral origin.8
There has been a sparsity of reports concerning the histopathology of the disease. Pels3 cites Kyrle's findings of "mild inflammatory reaction in the epithelium (spongiosis) including intraepithelial vesiculation." Also, he gives a more detailed
BUNCH LW, TILLEY JC. Pityriasis Rosea: A Histologic and Serologic Study. Arch Dermatol. 1961;84(1):79–86. doi:10.1001/archderm.1961.01580130085012
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