Vascular Ehlers-Danlos syndrome (vEDS) is a rare and severe connective tissue disorder caused by mutations in the collagen type III alpha I chain (COL3A1) gene. We describe a pathogenetic heterozygous COL3A1 mutation c. 3140 G>A, p. Gly1047Asp, identified using next-generation sequencing, in a 40-year-old Italian female. The genetic test performed on her relatives, which present different clinical phenotypes, confirmed that they carry the same mutation in heterozygous state. This finding confirms that mutations causing vEDS have an incomplete penetrance.