Abbreviations, DLB: Dementia with Lewy Bodies; AD: Alzheimer Disease; GFAP: glial fibrillary acidic protein; NfL: neurofilament light; Aβ42/40: amyloid β 1–42/ amyloid β 1–40 ratio; pTau231: phosphorylated Tau 231; pTau181: phosphorylated Tau 181; MTA: medial temporal lobe atrophy; GCA-F: global cortical atrophy scale – frontal subscale; PA: posterior atrophy. The gene discussed is GFAP; the disease is early-onset autosomal dominant Alzheimer disease.