The relative small number of families described to date, combined with a high level of clinical heterogeneity between and within families (Kuo et al., 2012; Vahedi and Alamowitch, 2011) and focus on the cerebrovascular disease aspects of Col4a1 disease, can all explain why these phenotypes have yet to emerge and highlight the need for a further detailed clinical analysis of affected individuals. This evidence concerns the gene COL4A1 and cerebrovascular disorder.