Wolf's isotopic response

The term "isotopic response" was coined by Wolf et al in 1995 to describe the occurrence of a new skin disorder at the site of another unrelated and already healed skin disease. When this term was found to be unsuitable for Medline searches because it generated hundreds of references that were linked with radioactive isotopes, it was changed to "Wolf's isotopic response" and eventually included as such in Stedman's Illustrated Dictionary of Dermatology Eponyms. Our search of the literature yielded 176 cases of Wolf's isotopic response. We describe this entity and present representative clinical examples. Some problems in the definition of Wolf's isotopic response are provided with special emphasis on its overlapping with the Koebner isomorphic response, a similar, but different, phenomenon. Also addressed are a number of issues associated with another term, "isotopic nonresponse," which had been introduced in analogy to the "isomorphic nonresponse" for describing the absence of an eruption at the site of another unrelated and already healed skin disease, or the sparing of the sites of another unrelated and already healed skin disease. In the spirit of the present issue, this contribution discusses only the clinical morphology and not the etiology, pathomechanism, or molecular biology of Wolf's isotopic response.