A pathergic response to fractional CO2.

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.