Cutaneous mosaicisms: concepts, patterns and classifications.
Bottom Line: A mosaic is an organism composed of two or more genetically distinct cell populations derived from a genetically homogeneous zygote.Cutaneous mosaicisms are the clinical expressions of these disorders.The main event which allows the existence of mosaicism is a genetic mutation, either structural or functional.
Affiliation: University of Brasilia, BrasiliaDF.
A mosaic is an organism composed of two or more genetically distinct cell populations derived from a genetically homogeneous zygote. Cutaneous mosaicisms are the clinical expressions of these disorders. The main event which allows the existence of mosaicism is a genetic mutation, either structural or functional. Cutaneous mosaicisms usually manifest by specific patterns on the skin and the archetypic pattern is the system of Blaschko lines, but others include checkerboard, phylloid, large patches without midline separation and lateralization. Since 1901, when Blaschko lines were first described, the study of mosasicism has helped to elucidate the behavior of numerous genetic diseases, generating therapeutic perspectives for these pathologies, including the promising gene therapy.
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Mentions: Verrucous epidermal nevus originate from keratinocyte hyperplasia, and arecharacterized by brown or skin-colored papules and/or plaques, with a verrucousor velvety surface, appearing linearly, following the Blaschko lines (Figures 7A and 7B). On flexor surfaces and osseous prominences, these nevican become more hyperkeratotic (Figure8). In rare cases, it is possible for basal cell carcinomas,keratocanthomas, spinocellular carcinomas, and malignant eccrine poromas todevelop, though these are rarer than with the other epidermal nevi (sebaceousand apocrine). Today, it is known that up to 33% of verrucous epidermal neviare due to mutations in the FGFR3 gene, which is also responsible for thedevelopment of seborrheic keratoses.1