Although structural disease of blood vessels contributes to cerebral hypoperfusion in at least some patients with AD, we did not find Aβ amyloid angiopathy, SVD or reduced microvessel density to contribute significantly to the reduction in MAG:PLP1 in the frontal cortex, medial parietal cortex or parietal white matter in most cases [11, 106, 158]. The gene discussed is PLP1; the disease is Alzheimer disease.