The interpretation of genetic variants in MBTPS2 is complicated by the gene’s pleiotropic properties; MBTPS2 variants can also cause the dermatological conditions Ichthyosis Follicularis, Atrichia and Photophobia (IFAP), Keratosis Follicularis Spinulosa Decalvans (KFSD) and Olmsted syndrome (OS) without skeletal abnormalities typical of OI. This evidence concerns the gene MBTPS2 and keratosis follicularis spinulosa decalvans.