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: The cutaneous findings are specific to the syndrome and occur in 96% of cases.They are usually divided into four stages, which can be concomitant orsequential: stage 1- during birth or the first months of life, characterized bylinear inflammatory vesicles and bullae that can last weeks to months; stage 2-linear verrucous hyperkeratotic plaques appear (they can last several months);stage 3- brown or grey-blue, superimposed pigmentation can emerge, distributedalong the Blaschko lines or appearing as "Chinese characters", which tends tofade slowly until it disappears in adulthood; and lastly, stage 4- linearhypopigmented macules, with loss of cutaneous appendages in the midsection andlimbs, in adulthood (Figure11).19,20