COL4A1 and porencephaly: Over the years, variants in COL4A1 have been identified in a wide range of diseases, including porencephaly,16 familial and sporadic small vessel disease and hemorrhagic stroke,15,17,18 leukoencephalopathy,19 HANAC syndrome,10 Walker-Warburg syndrome,21 and isolated ophthalmologic anomalies.19–21COL4A1-related disorders represent a single disease with great variability in expressivity and age at onset.