In the Alzheimer’s Biomarker Consortium-Down Syndrome study (ABC-DS; n = 242; age = 25–72), we estimated the age inflection point at which MRI-based white matter hyperintensities (WMH), enlarged perivascular spaces (PVS), microbleeds, and infarcts emerge in relation to demographic data, risk factors, amyloid and tau, and AD diagnosis. Here, MAPT is linked to Down syndrome.