We propose that extensive dermal melanocytosis and PPV are members of an expanding group of heterotrimeric G-protein alpha subunit gene mosaic conditions, joining McCune-Albright syndrome (Weinstein et al., 1991), caused by mosaicism for gain-of-function mutations in GNAS, and SWS, caused by mosaic gain-of-function mutations in GNAQ (Shirley et al., 2013). This evidence concerns the gene GNAS and McCune-Albright syndrome.