FBN1 and Marfan syndrome: This finding did not override either the previous clinical diagnosis of MFS or the presence of a mutation in the three major genes, due to several potential explanations: presence of (1) a large insertion/deletion involving several exons or the entire candidate genes (FBN1 or TGFBR2 or TGFBR1) [38–42] and (2) mosaicism in the three major genes [42–48].