WES identified a heterozygous mutation in COL4A1, which is known to cause a cerebral small vessel disease (SVD) with symptoms including transient ischaemic attacks, adult-onset haemorrhagic stroke, periventricular brain abnormalities, white matter hyperintensities and leukoencephalopathy (including cerebellar hypoplasia, cerebral atrophy and vascular changes) [51–53]. The gene discussed is COL4A1; the disease is cerebral small vessel disease.