Efflorescence of new warts: a sign of onset of involution in flat warts.

The sudden eruption of large numbers of tiny new warts in a patient with multiple flat warts often signals the onset of involution and subsequent regression of all flat warts. We have observed 5 such cases and, in this report, describe 2 cases in which the sudden efflorescence of many new warts was used as a sign to predict accurately the onset of involution and subsequent regression of all flat warts. Correlation of the histopathological and clinical findings provides an explanation for this phenomenon.