The phenomenon of spontaneous regression of numerous flat warts: immunohistological studies.

The phenomenon of systemic regression of numberous flat warts takes place within one month after the sudden onset of spontaneous inflammation in them. In other types of warts, we have never observed such a dramatic regression. We performed a histological study in a total of 51 cases showing this spontaneous inflammation in their flat warts and found a massive mononuclear cell infiltration in all. In 9 cases, a histological study for basophils was carried out but failed to show them among the infiltrating cells despite the strong histological resemblance to contact allergy. An immunofluorescence technique performed in 16 cases demonstrated no specific deposits of immunoglobulins and complement in such inflamed wart tissues except for those which appear to be only a secondary event to inflammation per se. These immunopathological findings further substantiate the concept that cell-mediated mechanisms rather than humoral immunity play a major role in this phenomenon of sudden regression of numerous flat warts.