Given that mutations in TMEM5 have recently been described as being causal for CMD and that the putative enzyme shows sequence homology to glycosyltransferases (Vuillaumier-Barrot et al., 2012; Jae et al., 2013), we explored the possibility that TMEM5 was a xylose transferase (Figure 5). Here, RXYLT1 is linked to congenital muscular dystrophy.