Development of a keratoacanthoma after topical photodynamic therapy with 5-aminolevulinic acid.

Since its FDA approval in 1999, photodynamic therapy (PDT) with topical 5-aminolevulinic acid has become an increasingly popular modality for the treatment of actinic keratosis (AKs). It is hoped that in addition to improving clinical signs and symptoms of AKs, PDT might prevent the development of skin cancer. We present a case of a patient developing a keratoacanthoma immediately following PDT for AKs.