When Epstein and Kligman1 described the treatment of warts with cantharidin they mentioned as an unusual complication a "rapid growth of the wart to occupy the entire blister site. A `doughnut' formed, with apparent central clearing and a peripheral ring of exuberant new wart."
The accompanying illustration shows a well marked example of this phenomenon. It comes from a 17-year-old girl whose forearm was treated for about 10 small warts with Kligman's 0.7 per cent cantharidin varnish. Large blisters, one with pseudopodia, resulted. These were not drained but were treated by occlusion with a fatty gauze dressing. The dry blisters peeled and six weeks later the picture of polycyclic and circinate patterns of wart papules was seen, showing in one
Gyrate, circinate, and iris arrangement of warts in the pattern of preceding cantharidin blistering. lesion an iris arrangement through persistence in the center of the original
FINDLAY GH. Wart Relapses at the Edges of Therapeutic Cantharidin Blisters. AMA Arch Derm. 1959;80(5):589–590. doi:10.1001/archderm.1959.01560230075019
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