A Pathergic Response to Fractional CO2

September 2012 | Volume 11 | Issue 9 | Case Reports | 1122 | Copyright © September 2012

Pathergy is a nonspecific response to stimuli seen in a multitude of disease states. We present what we feel is a unique variant of this phenomenon, a case of multiple keratoacanthomas developing following treatment with Fractional CO2. This state of acute tumor emergence, which is similar to an isomorphic response, is believed to be related to changes in both the inflammatory and immune response. It is imperative that one keeps this process in their differential when evaluating a patient that has not only a potential predisposing disease, but also a history of traumatic exposure.

J Drugs Dermatol. 2012;11(9):1122-1123.


It is well known that many disease processes manifest in areas of trauma. For example, psoriasis can occur in predisposed individuals from an inciting event such as an excoriation. This type of reaction is known as an isomorphic response, or Koebnerization. True Koebnerization is an abnormal response in which a particular disease entity manifests at sites of trauma; Koebnerization is specific to each disease process, and will therefore differ slightly between dermatologic conditions. In the case of keratoacanthomas, which are rapidly growing cutaneous tumors believed to arise from hair follicles, koebnerization is a process not typically ascribed; however, cases exemplifying this phenomenon are well documented. Interestingly, a similar but unique process known as pathergy, which is also related to skin trauma, is well documented and commonly mistaken for Koebnerization. Unlike Koebnerization, pathergy is a nonspecific response to stimuli, and is seen in a multitude of disease states.
A broad variety of dermatologic conditions, including psoriasis, lichen planus, and non-melanoma skin cancer are all well documented in the literature as being associated with pathergy. The inciting events include not only varying degrees of cutaneous trauma, but also topical immunomodulators such as imiquimod. Our discussion will focus on an eruption of keratoacanthoma- like lesions which, occurring after a traumatic cosmetic procedure, are believed to be pathergic in nature.


A Caucasian female, aged 67 years, presented following treatment for dermatoheliosis. She had previously been unsatisfied with the appearance of her skin and sought options for improved cosmesis. Following a comprehensive examination, Fractional CO2 was selected to treat the dorsal aspect of her hands. The patient tolerated this procedure well, noting only minimal erythema and scaling during the first post-operative week. At approximately day 10 this eruption progressed, however, revealing multiple erythematous papules and pustules. A secondary infection was suspected at this time, and as a result she was treated with both topical and oral antibiotics.
Despite antibiotic therapy the patient's condition continued to progress, with the development of multiple eruptive craters on the areas described above. Although essentially asymptomatic, their abrupt and unsightly nature prompted her to again seek medical attention. Evaluation at this time demonstrated multiple discrete erythematous papules with central keratin cores—consistent with a diagnosis of squamous cell carcinoma, keratoacanthoma-type (Figures 1 and 2). This diagnosis was confirmed by histopathology (Figure 3), following which these tumors were treated successfully with electrodessication and curettage.


This case demonstrates a unique variant of a well-documented entity know as pathergy, in which the application of a stimulus leaves one unduly susceptible to subsequent stimuli of a different kind. For example, in Sweet's syndrome, often associated with malignant and paraneoplastic conditions, a patient may develop multiple papular lesions at sites of venipuncture or peripheral intravenous access. Although often thought to be synonymous with koebnerization, pathergy differs in that it is a nonspecific response to a stimulus. Resulting conditions include non-melanoma skin cancer, psoriasis, and pyoderma gangrenosa, as well as lichen planus, Sweet's syndrome, Behcet syndrome, and vitiligo.
The initial inciting stimulus is classically a traumatic event such as a needle-stick, cutaneous surgery, or a fall. Quite predictably, within a well-defined amount of time and at fairly well localized