We present details of a neonate with extensive naevus sebaceus in whom we identified a pathogenic mutation in HRAS (c.37G > C; p.Gly13Arg), but only in lesional skin DNA, consistent with a mosaic RASopathy.
Focused amplicon deep sequencing on DNA extracted from the brain tumor and a cutaneous nevus revealed a heterozygous (c.37G>C; p.G13R) substitution in the NRAS gene.
Nine cases presented concomitant BRAF and NRAS mutations, including one case in which both the melanoma and the adjacent naevus harboured V600E and Q61K double mutations.