Nevus sebaceus is a mosaic RASopathy.

The recent discovery that nevus sebaceus is a mosaic RASopathy represents a major breakthrough in research on epidermal nevi. In this issue, both Levinsohn et al. and Sun et al. confirm this advancement with results obtained through whole-exome sequencing. Further molecular studies will almost certainly show that sebaceous and keratinocytic nevi are different disorders, although there is some clinical overlap.