Features of hypopigmented verruca plana in reflectance confocal microscopy and comparative analysis of hypopigmented and classic verruca plana in children

Verruca plana (VP) is an intraepidermal tumor caused papilloma virus infection. Most VP in the clinic is the classic type, which is characterized by a slightly elevated, flattopped papule, and hypopigmented VP is rare. In contrast to classic VP, hypopigmented VP is characterized by white maculopapules that sometimes show Koebner's phenomenon, mostly occurs on children's foreheads and other exposed areas, and is rarely seen in adults. However, as there have been few studies on this issue1 and biopsy (which is invasive and associated with injuries, pain, and scars) is not always possible for outpatients, especially pediatric patients, dermatologists frequently cannot diagnose it based on their own experience. Reflectance confocal microscopy (RCM) is a powerful, noninvasive, repetitive imaging tool that provides realtime images at a nearly cellular histological resolution. The application value of RCM in pigmented diseases, inflammatory diseases, and tumors has been widely recognized.24 Additionally, the typical RCM features of classic VP have been widely acknowledged,5,6 but there have been few studies on RCM findings in hypopigmented VP. Thus, we sought to clarify the main identifying characteristics of hypopigmented VP with RCM, the corresponding relationship between RCM image features and dermatopathology, and differences between classic VP and hypopigmented VP in children.