Any porencephaly in which the cause of the disease is a mutation in the COL4A1 gene. The disease is brain small vessel disease 1 with or without ocular anomalies (MONDO_0008289, a Monarch Disease Ontology term). Also known as: ADT1P, BSVD, BSVD1, COL4A1 porencephaly, COL4A1-related brain small vessel disease with haemorrhage, COL4A1-related brain small vessel disease with hemorrhage, COL4A1-related familial vascular leukoencephalopathy, COL4A1-related retinal arteriolar tortuosity-infantile hemiparesis-autosomal dominant leukoencephalopathy syndrome.