We report on the case of a 44-year-old man affected with the Simpson-Golabi-Behmel syndrome (SGBS) (OMIM 312870) presenting with ischemic stroke due to a dissection of the right internal carotid. Molecular genetic analysis revealed the p.Gly556Arg mutation in exon 8 of the gene encoding glypican 3 (GPC3). This is the second case of a GPC3 missense mutation to be reported. The only risk factor found in this patient was carotid redundancy, a deformation that is significantly associated with spontaneous carotid dissection. The natural history of SGBS in adults is poorly known, and this case raises the question of a possible vascular risk associated with the disease.