Plasma NfL was greater in the Alzheimer’s disease group (19.44 ± 11.36 pg/mL, P < 0.001), the SIVD group (21.85 ± 10.00 pg/mL, P < 0.001) and the FTLD group (24.01 ± 14.17 pg/mL, P < 0.001) than in the CU group (11.23 ± 7.85 pg/mL). The gene discussed is NEFL; the disease is early-onset autosomal dominant Alzheimer disease.