Koebner's sheep in Wolf's clothing: does the isotopic response exist as a distinct phenomenon?

Abstract

Until 1995, a case of psoriasis developing within the dermatome of a healed herpes zoster was taken as a Koebner phenomenon. In this year, however, the term 'isotopic response' was introduced by Wolf et al. to describe 'the occurrence of a new skin disorder at the site of another, unrelated and already healed skin disease', thus appearing 'on apparently unaffected and healthy skin'. Initially, the term was mainly related to herpes zoster, but today the name 'Wolf's isotopic response' is used to include a plethora of other triggering factors such as healed cutaneous leishmaniasis, tinea or varicella. For obvious reasons, such triggering factors cannot be taken as examples of 'unaffected and healthy skin'. Notably, the authors themselves have categorized the dermatome of a healed herpes zoster as a 'vulnerable area'. In a recent commentary, Wolf et al. have expanded the definition of healed skin diseases triggering an 'isotopic response'. They now included 'scars, pigment changes, color changes or various other minimal changes by the first disease'. Hence, there is no clear-cut criterion to distinguish the isotopic response from a Koebner reaction. Wolf et al. even argue that, if the triggered disorder precedes the appearance of generalized skin lesions, then it is not a Koebner reaction but 'Wolf's isotopic response'. In our view, such definition is unacceptable. All reactions of this kind represent examples of a Koebner phenomenon. Accordingly, the 'isotopic response' should today be taken as a historical error.

Nummular eczema and isomorphic Koebner response

“…Eczema is included in the fourth category, along with a number of other conditions. By contrast, the cases of NE on the scar sites in the current study suggest that KR can result in NE, because injured skin is not normal and thus is susceptible to developing other lesions 2 . A recent study reported that out of 1662 patients who had undergone breast reconstruction, 48 developed NE, 3 which both occurred in periwound and nonperiwound regions, and in some of the cases, the lesions developed on the operation scar.…”

Flag‐like hypermelanosis with superimposed lichen sclerosus et atrophicus: an unusual Koebner phenomenon?

“…The conspicuous colocalization of EG‐LSA with pre‐existent mosaic hypermelanosis may be best explained as a Koebner phenomenon 1 . The term ‘Wolf’s isotopic response’ should be avoided for such colocalization since, in our view, this term reflects a historical error 6 …”

Annular elastolytic giant cell granuloma following herpes zoster infection

“…4 Actually, the term Wolf's isotopic response is not approved by all physicians and it is till matter of discussion if this phenomenon should be classified as a variant of the Koebner (isomorphic) response. 5 Its pathogenesis is currently unknown. Some authors suggested that it might be due to viral particles that remain in the tissue and are responsible for the onset of the subsequent disease.…”