While APOE and ApoA1 are the most abundant apolipoproteins in the CSF and highly enriched in the brain (Borghini et al, 1995; Koch et al, 2001), APOC1—a less‐abundant brain apolipoprotein—was implicated in Alzheimer disease although its regulation and possible role is poorly understood (Petit‐Turcotte et al, 2001). This evidence concerns the gene APOC1 and early-onset autosomal dominant Alzheimer disease.