Intriguingly, APOE4 has also been associated with higher levels of CSF α-syn in patients in the AD continuum where patients with mild cognitive impairment (MCI) who, after 24 months follow-up fulfilled the clinical criteria for an AD diagnosis, exhibited higher CSF α-syn levels in an APOE4 dose-dependent manner [685]. The gene discussed is APOE; the disease is Alzheimer disease.