FBN1 and Marfan syndrome: MFS is caused by mutations in fibrillin 1 (FBN1; MIM 134797) (Lee et al., 1991), identified in 90%–95% of individuals who meet the revised Ghent criteria (acknowledging that a FBN1 mutation is among those criteria) (Baetens et al., 2011; Loeys et al., 2004, 2010; Robinson et al., 2006).