COL4A1 and autosomal dominant familial hematuria-retinal arteriolar tortuosity-contractures syndrome: The proportion of cases caused by a de novo pathogenic variant is estimated to be at least 27%–54%.2,3 Phenotypes include porencephaly type 1 (Online Mendelian Inheritance in Man [OMIM]# 175780), brain small vessel disease with or without ocular anomalies (OMIM# 607595), tortuosity of retinal arteries (OMIM# 180000), and hereditary angiopathy with nephropathy, aneurysms, and muscle cramps (HANAC) (OMIM# 611773).4,5 Intrafamilial and interfamilial variability are common findings in all COL4A1-related disorders.