CSF biomarker levels were analyzed in Alzheimer’s disease–ep patients, and age- and sex-matched controls (NfL: n = 226, GFAP: n = 83, T-tau: n = 384, P-tau: n = 364, Aβ42: n = 364 per group). Here, GFAP is linked to early-onset autosomal dominant Alzheimer disease.