The percentage of GFAP astrogliosis burden was lowest in the hippocampus of hippocampal sparing AD (median [IQR], 13% [8.5%-18%]) but plateaued in typical AD (median [IQR],33% [22%-43%]; post hoc P < .001) and limbic predominant AD (median [IQR], 30% [28%-40%]; post hoc P < .001) relative to monotonic increase in percentage of GT-38 burden. Here, GFAP is linked to Alzheimer disease.