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. In this consensus expert review as part of the European Reference Network project (ERN-Skin), we lay out the general principles of mosaicism as they are currently understood, summarise 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 suspected mosaic patient. This article is protected by copyright. All rights reserved.