RT Journal Article SR Electronic T1 Mosaicism for oncogenic G12D KRAS mutation associated with epidermal nevus, polycystic kidneys and rhabdomyosarcoma JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 859 OP 862 DO 10.1136/jmg.2009.075374 VO 47 IS 12 A1 Franck Bourdeaut A1 Aurélie Hérault A1 David Gentien A1 Gaëlle Pierron A1 Stelly Ballet A1 Stéphanie Reynaud A1 Régine Paris A1 Gudrun Schleiermacher A1 Clarisse Baumann A1 Pascale Philippe-Chomette A1 Marion Gauthier-Villars A1 Michel Peuchmaur A1 François Radvanyi A1 Olivier Delattre YR 2010 UL http://jmg.bmj.com/content/47/12/859.abstract AB Background Epidermal nevus (EN) is a congenital disorder characterised by hyperpigmented epidermal thickening following a Blaschko's line. It is due to somatic mutations in either FGFR3 or PIK3CA in half of the cases, and remains of unknown genetic origin in the other half. EN is also seen as part of complex developmental disorders or in association with bladder carcinomas, also related to FGFR3 and PIK3CA mutations. Mosaic mutations of these genes have been occasionally found in syndromic EN.Case report The co-occurrence of EN, rhabdomyosarcoma, polycystic kidneys and growth retardation in an infant is described.Results An oncogenic G12D KRAS mutation was detected in both the epidermal component of the EN and in the rhabodmyosarcoma but not in the dermal component of the EN lesion or in unaffected tissues, including normal skin or blood.Conclusion This report shows for the first time that a KRAS mutation in epiderma causes EN. Observation of the same G12D KRAS mutation in two distinct regions of the body strongly suggests a somatic mosaicism. Finally, this report highlights the potentially underestimated importance of mosaic oncogene mutations in childhood cancers.