COL4A1 and cerebrovascular disorder: Rare mutations that most frequently affect Gly residues in the Gly-Xaa-Yaa repeat in COL4A1/A2 cause mendelian early-onset cerebrovascular disease, ocular dysgenesis, and myopathy.8, -, 12 However, the full spectrum of effects of COL4A1/A2 mutations remain incompletely characterized.7,13,14 Sequencing of a few families or small number of patients (n < 100) suggested rare variants in COL4A1/A2 can contribute to sporadic ICH.9, -, 15