Marfan and Loeys–Dietz syndromes are connective tissue disorders characterized by high clinical variability. The major morbidity and mortality in both syndromes relate to the dilatation of the aorta predisposing to aortic tear. We investigated the putative relationship between the genotype, aortic growth speed and the occurrence of severe cardio vascular events (prophylactic surgery of the aortic root, aortic dissection or related death).

We have performed a retrospective study of 102 patients with pathogenic variants in FBN1, TGFβR1 and R2 and SMAD3 genes followed at a Marfan reference center in France. The average age at the start of the study was 13.8years and data were collected over 5years. The FBN1 variants were classified as haploinsufficient (HI) or dominant negative (DN). Aortic diameters and aortic dilatation at the level of the Valsalva sinuses were assessed by echocardiography.

No overall aortic growth difference was found between Marfan and Loeys–Dietz syndrome (1.14 vs. 1.11mm/year, P=0.74), neither between HI and DN groups (1.12 vs. 1.01mm/year, P=0.36). However, patients with a SMAD 3 mutation seem to have lower aortic growth than those in the TGFβ group (0.91 vs. 1.34mm/year, P=0.36). No difference concerning Valsalva sinus Z score evolution was found between these groups. We did not find any differences concerning the occurrence of cardio vascular events between Marfan and Loeys–Dietz syndrome and their genetics subgroups. Aortic growth in men was significantly faster than in women (1.23 vs. 0.91mm/year, P=0.005).

Marfan syndrome and Loeys–Dietz, as well as their genetics subgroups should be monitored similarly for the development of aortic root aneurysm. Like other phenotypic characteristics of these syndromes, the cardio vascular manifestations present a high variability among patients and a correlation genotype/phenotype is not informative for patient care. A possible exception is the TGFβ group, which may grow faster.