Hereditary cerebral small vessel diseases (CSVDs) include cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) caused by NOTCH3, cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy caused by biallelic HTRA1, and heterozygous HTRA1-related CSVD. This evidence concerns the gene HTRA1 and CADASIL.