Response to Choi et al, “Pathergy beyond neutrophilic dermatoses: A case of localized leukemia cutis at the site of intravenous infiltration”

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To the Editor:

We commend Choi et al1 for their insightful report, “Pathergy beyond neutrophilic dermatoses: A case of localized leukemia cutis at the site of intravenous infiltration.” The case adds valuable perspective to the spectrum of leukemia cutis presentations. However, we believe the term pathergy is inappropriately applied in this context.

Pathergy, by definition, refers to a sterile, nonspecific hypersensitivity reaction to minor trauma, most commonly associated with neutrophilic dermatoses such as pyoderma gangrenosum and Sweet syndrome.2 Histopathologically, pathergy demonstrates a neutrophil-predominant infiltrate without true vasculitic features.3 The presence of methicillin-susceptible Staphylococcus aureus and biopsy findings of atypical cells expressing CD33, CD117, and myeloperoxidase (consistent with leukemia cutis) argue against a pathergic process. The lesion described instead reflects leukemic infiltration arising at an infected, traumatized site.

The authors draw an analogy between leukemia cutis developing at a site of trauma and a pathergic response. However, these processes are distinct, and the terminology should reflect this distinction. This presentation may represent a Koebner phenomenon, in which new lesions of an existing skin disease appear at sites of trauma, or more likely an isotopic response, where a new condition (not necessarily a primary dermatosis) develops in previously traumatized skin.4^,^5 Each term—pathergy, Koebnerization, isotopic response—carries distinct definitions that should not be used interchangeably. Precise terminology remains essential, as dermatologic descriptors convey specific pathogenetic and diagnostic information that guide clinical interpretation.

Conflicts of interest

None disclosed.