Abstract
Background and Objectives Post-inflammatory hyperpigmentation (PIH) is a common adverse effect of laser hair removal procedures. This case series emphasizes the under-reported crescent-shaped form of PIH that may occur following laser therapy. This case series sought to assess the potential causes of the distinct, crescent-shaped form of PIH that may arise following laser hair removal procedures, and to examine the concept of thermal versus cryogenic damage, which was discovered accidentally due misalignments between laser-cryogen spurts. Study Design/Materials and Methods A retrospective, multicentre case recruitment was undertaken, involving three laser centers and presented in the form of a case series. The included patients were individuals with crescent-shaped PIH following laser hair removal. Results Fifteen patients were recruited over 12 months. All patients were treated with the GentleLase system (Candella) with built-in cryogen spurt. Prior to the study, only one patient had suffered from PIH following laser hair removal. Most patients improved partially or completely both with and without the use of bleaching compounds. After testing one machine, it was found that the cryogen spurt was misaligned. It was not located in the circle of the laser beam, thereby leaving a crescent shape of uncooled but laser-treated skin. A trial on one patient with cryogen alone did not cause PIH, whereas a trial with the laser alone caused PIH. Conclusion The appearance of crescent-shaped marks following PIH is a distinct and uncommon adverse effect associated with laser hair removal procedures. This case series suggests that it arises due to the malfunctioning of the built-in cryogen spurt device, leading to a deficit in cooling a portion of the treated skin, urging checking the built-in cryogen spurt device. Lasers Surg. Med. (c) 2020 Wiley Periodicals, LLC