HTRA1 and CARASIL: Thus, there are two possible phenotypes related to HTRA1 gene mutation: “classical” CARASIL syndrome, inherited in an autosomal recessive manner (MIM 600142), and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, type 2 (CADASIL2) or, alternatively, HTRA1-related cerebral small vessel disease (HTRA1-CSVD) (MIM 616779) [6,9].