MBTPS2 and Olmsted syndrome: Variants in the MBTPS2 gene have been reported to cause a broad phenotypic spectrum of X-linked genodermatosis, including the X-linked form of Olmsted syndrome and IFAP syndrome with or without BRESHECK syndrome.6MBTPS2 maps to chromosome Xp22.12-p22.11 and has 11 exons and encodes 2 isoforms, the longest of which is a 519 amino acid intramembrane zinc metalloprotease, which is essential for development.