Alternatively, the less common class of haploinsufficiency (decreased protein production from the mutated FBN1 gene on one, or rarely two, chromosomes) results in decreased amounts of normal Fbn-1 protein present in the ECM; compared with DN mutations, this class of defects carries greater risk of aortic aneurysm or vascular dissection (Franken et al., 2017). Here, FBN1 is linked to aortic aneurysm.