Mosaic abnormalities of the skin: review and guidelines from the European Reference Network for rare skin diseases

Background Cutaneous mosaicism is an area of dermatology in which there has been an explosion of knowledge within the current decade. This has led to fundamental changes in the understanding of the conditions in this field, and to an ongoing paradigm shift in the approach to management of mosaic skin disorders. Objectives To lay out the general principles of mosaicism as they are currently understood, summarize the known cutaneous mosaic abnormalities of the skin with associated phenotypic and genotypic information, review the latest trials on targeted therapies and propose guidelines for the general approach to a patient with suspected mosaicism. Methods This was a consensus expert review as part of the European Reference Network project (ERN-Skin). Conclusions This study provides clinicians with a practical approach to the patient with suspected mosaicism, redefines mosaicism for the modern genetic era, and proposes a new classification system based on genetic mechanism.