Clinical and genetic data of 20 new patients with SMAD3 mutations, type 3 Loeys Dietz Syndrome (LDS), and reviews of the literature

Abstract

Pathogenic variants in SMAD3 (type 3 LDS, Marfan-like connective tissue disorder) cause thoracic aortic aneurysms and dissections, along with aneurysms and rupture of other arteries. Generally, these aggressive vascular damages are associated with multisystemic signs including skeletal abnormalities and premature osteoarthritis. Variable expressivity and incomplete penetrance are commonly associated. Aortic status, events, and clinical features were abstracted through retrospective review of medical records 20 new patients (28.8 years-old (6–60)) from 8 families from our Reference Centre. After a complete review of the literature, we collected a total of 49 unique variants of different nature (missense, truncating and splicing variants) from 152 individuals of 58 unrelated families. The aim of this study was to look for genotype-phenotype correlations between the mutations of this gene and the severity of the phenotype. Aortic aneurysm and/or dissection are the main vascular findings, affecting respectively 57% and 32% of all type 3 LDS patients described. In our cohort of patients, half presents an aortic dilatation (10/20), 10% an aortic dissection. Three of our patients displays an aortic dilatation during their childhood (at 8 and 7-years-old and a surgery for an aortic dilation at 10-years-old). Aneurysms and dissections can also be seen in other arteries in 27% (35/138) and particularly intracranial aneurysms found in 20% of patients (21/103), like in two of our patients, one presented an iliac artery dissection. Arterial tortuosity is also frequent, particularly in carotids, representing about a third of the patients (36/117 = 31%), 2 of our 8 patients. SMAD3 pathogenic variants cause thoracic aortic aneurysms and dissections in the majority of individuals with variable age of onset and reduced penetrance. We confirmed that there is no correlation between the mutation type and the phenotype severity.