A second genotype-specific presentation is of occlusive cerebrovascular disease (stenosis, aneurysms, moyamoya) as a feature of SAMHD1 (SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase)-related disease, sometimes in the absence of any other stigmata (49) (Figure 2E). The gene discussed is SAMHD1; the disease is aneurysm.