MBTPS2 and osteogenesis imperfecta: More recently several other recessive forms of OI- TMEM38B/BMP1/CREB3L1/SPARC have been characterised (Shaheen et al., 2012; Martínez-Glez et al., 2012; Symoens et al., 2013; Mendoza-Londono et al., 2015) and X-linked forms of OI (PLS3/MBTPS2) (van Dijk et al., 2009; Lindert et al., 2016) and heterozygous variants in WNT1/LRP5 (Laine et al., 2012; Hartikka et al., 2005) making OI a very genetically heterogeneous condition and perhaps use of heritable bone fragility as a more appropriate terminology to describe this group of conditions.