Characterization of Post-Inflammatory Hyperpigmentation related to Acne by Reflectance Confocal Microscopy: Morphological and structural aspects

Post-Inflammatory Hyperpigmentation (PIH) is a common pigmentary disorder in patients with pigmented skin. Histological and clinical exams have been used for the diagnosis of PIH and to determine the correct treatment. However, Reflectance Confocal Microscopy (RCM) has the potential to replace these methods since it is a noninvasive advanced technique and has a higher diagnostic accuracy than dermatoscopy. The aim of this study was to characterize PIH and correlate the main aspects observed by RCM with the macroscopic characteristics of acne-related PIH. Thus, 12 subjects with previously diagnosed acne and PIH were selected for the study. PIH was evaluated by RCM. The brightness of the basal cell layer, the dermal-epidermal junction (DEJ) thickness, and the depth of dermal papillae were quantified and the morphological and structural features of the DEJ were analyzed. The results showed an increase of epidermal pigmentation, a reduction of DEJ thickness, and no change in epidermal thickness. Melanophages were observed in the papillary dermis, as well as changes in the size and shape of dermal papillae. Finally, the study describes the characteristics of PIH and can help dermatologists to diagnose PIH with an innovative method that reduces the stress associated with a histological biopsy.